diff --git a/vendor/go.uber.org/zap/zapcore/json_encoder.go b/vendor/go.uber.org/zap/zapcore/json_encoder.go
new file mode 100644
index 0000000..9aec4ea
--- /dev/null
+++ b/vendor/go.uber.org/zap/zapcore/json_encoder.go
@@ -0,0 +1,505 @@
+// Copyright (c) 2016 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package zapcore
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"math"
+	"sync"
+	"time"
+	"unicode/utf8"
+
+	"go.uber.org/zap/buffer"
+	"go.uber.org/zap/internal/bufferpool"
+)
+
+// For JSON-escaping; see jsonEncoder.safeAddString below.
+const _hex = "0123456789abcdef"
+
+var _jsonPool = sync.Pool{New: func() interface{} {
+	return &jsonEncoder{}
+}}
+
+func getJSONEncoder() *jsonEncoder {
+	return _jsonPool.Get().(*jsonEncoder)
+}
+
+func putJSONEncoder(enc *jsonEncoder) {
+	if enc.reflectBuf != nil {
+		enc.reflectBuf.Free()
+	}
+	enc.EncoderConfig = nil
+	enc.buf = nil
+	enc.spaced = false
+	enc.openNamespaces = 0
+	enc.reflectBuf = nil
+	enc.reflectEnc = nil
+	_jsonPool.Put(enc)
+}
+
+type jsonEncoder struct {
+	*EncoderConfig
+	buf            *buffer.Buffer
+	spaced         bool // include spaces after colons and commas
+	openNamespaces int
+
+	// for encoding generic values by reflection
+	reflectBuf *buffer.Buffer
+	reflectEnc *json.Encoder
+}
+
+// NewJSONEncoder creates a fast, low-allocation JSON encoder. The encoder
+// appropriately escapes all field keys and values.
+//
+// Note that the encoder doesn't deduplicate keys, so it's possible to produce
+// a message like
+//   {"foo":"bar","foo":"baz"}
+// This is permitted by the JSON specification, but not encouraged. Many
+// libraries will ignore duplicate key-value pairs (typically keeping the last
+// pair) when unmarshaling, but users should attempt to avoid adding duplicate
+// keys.
+func NewJSONEncoder(cfg EncoderConfig) Encoder {
+	return newJSONEncoder(cfg, false)
+}
+
+func newJSONEncoder(cfg EncoderConfig, spaced bool) *jsonEncoder {
+	return &jsonEncoder{
+		EncoderConfig: &cfg,
+		buf:           bufferpool.Get(),
+		spaced:        spaced,
+	}
+}
+
+func (enc *jsonEncoder) AddArray(key string, arr ArrayMarshaler) error {
+	enc.addKey(key)
+	return enc.AppendArray(arr)
+}
+
+func (enc *jsonEncoder) AddObject(key string, obj ObjectMarshaler) error {
+	enc.addKey(key)
+	return enc.AppendObject(obj)
+}
+
+func (enc *jsonEncoder) AddBinary(key string, val []byte) {
+	enc.AddString(key, base64.StdEncoding.EncodeToString(val))
+}
+
+func (enc *jsonEncoder) AddByteString(key string, val []byte) {
+	enc.addKey(key)
+	enc.AppendByteString(val)
+}
+
+func (enc *jsonEncoder) AddBool(key string, val bool) {
+	enc.addKey(key)
+	enc.AppendBool(val)
+}
+
+func (enc *jsonEncoder) AddComplex128(key string, val complex128) {
+	enc.addKey(key)
+	enc.AppendComplex128(val)
+}
+
+func (enc *jsonEncoder) AddDuration(key string, val time.Duration) {
+	enc.addKey(key)
+	enc.AppendDuration(val)
+}
+
+func (enc *jsonEncoder) AddFloat64(key string, val float64) {
+	enc.addKey(key)
+	enc.AppendFloat64(val)
+}
+
+func (enc *jsonEncoder) AddInt64(key string, val int64) {
+	enc.addKey(key)
+	enc.AppendInt64(val)
+}
+
+func (enc *jsonEncoder) resetReflectBuf() {
+	if enc.reflectBuf == nil {
+		enc.reflectBuf = bufferpool.Get()
+		enc.reflectEnc = json.NewEncoder(enc.reflectBuf)
+
+		// For consistency with our custom JSON encoder.
+		enc.reflectEnc.SetEscapeHTML(false)
+	} else {
+		enc.reflectBuf.Reset()
+	}
+}
+
+func (enc *jsonEncoder) AddReflected(key string, obj interface{}) error {
+	enc.resetReflectBuf()
+	err := enc.reflectEnc.Encode(obj)
+	if err != nil {
+		return err
+	}
+	enc.reflectBuf.TrimNewline()
+	enc.addKey(key)
+	_, err = enc.buf.Write(enc.reflectBuf.Bytes())
+	return err
+}
+
+func (enc *jsonEncoder) OpenNamespace(key string) {
+	enc.addKey(key)
+	enc.buf.AppendByte('{')
+	enc.openNamespaces++
+}
+
+func (enc *jsonEncoder) AddString(key, val string) {
+	enc.addKey(key)
+	enc.AppendString(val)
+}
+
+func (enc *jsonEncoder) AddTime(key string, val time.Time) {
+	enc.addKey(key)
+	enc.AppendTime(val)
+}
+
+func (enc *jsonEncoder) AddUint64(key string, val uint64) {
+	enc.addKey(key)
+	enc.AppendUint64(val)
+}
+
+func (enc *jsonEncoder) AppendArray(arr ArrayMarshaler) error {
+	enc.addElementSeparator()
+	enc.buf.AppendByte('[')
+	err := arr.MarshalLogArray(enc)
+	enc.buf.AppendByte(']')
+	return err
+}
+
+func (enc *jsonEncoder) AppendObject(obj ObjectMarshaler) error {
+	enc.addElementSeparator()
+	enc.buf.AppendByte('{')
+	err := obj.MarshalLogObject(enc)
+	enc.buf.AppendByte('}')
+	return err
+}
+
+func (enc *jsonEncoder) AppendBool(val bool) {
+	enc.addElementSeparator()
+	enc.buf.AppendBool(val)
+}
+
+func (enc *jsonEncoder) AppendByteString(val []byte) {
+	enc.addElementSeparator()
+	enc.buf.AppendByte('"')
+	enc.safeAddByteString(val)
+	enc.buf.AppendByte('"')
+}
+
+func (enc *jsonEncoder) AppendComplex128(val complex128) {
+	enc.addElementSeparator()
+	// Cast to a platform-independent, fixed-size type.
+	r, i := float64(real(val)), float64(imag(val))
+	enc.buf.AppendByte('"')
+	// Because we're always in a quoted string, we can use strconv without
+	// special-casing NaN and +/-Inf.
+	enc.buf.AppendFloat(r, 64)
+	enc.buf.AppendByte('+')
+	enc.buf.AppendFloat(i, 64)
+	enc.buf.AppendByte('i')
+	enc.buf.AppendByte('"')
+}
+
+func (enc *jsonEncoder) AppendDuration(val time.Duration) {
+	cur := enc.buf.Len()
+	enc.EncodeDuration(val, enc)
+	if cur == enc.buf.Len() {
+		// User-supplied EncodeDuration is a no-op. Fall back to nanoseconds to keep
+		// JSON valid.
+		enc.AppendInt64(int64(val))
+	}
+}
+
+func (enc *jsonEncoder) AppendInt64(val int64) {
+	enc.addElementSeparator()
+	enc.buf.AppendInt(val)
+}
+
+func (enc *jsonEncoder) AppendReflected(val interface{}) error {
+	enc.resetReflectBuf()
+	err := enc.reflectEnc.Encode(val)
+	if err != nil {
+		return err
+	}
+	enc.reflectBuf.TrimNewline()
+	enc.addElementSeparator()
+	_, err = enc.buf.Write(enc.reflectBuf.Bytes())
+	return err
+}
+
+func (enc *jsonEncoder) AppendString(val string) {
+	enc.addElementSeparator()
+	enc.buf.AppendByte('"')
+	enc.safeAddString(val)
+	enc.buf.AppendByte('"')
+}
+
+func (enc *jsonEncoder) AppendTime(val time.Time) {
+	cur := enc.buf.Len()
+	enc.EncodeTime(val, enc)
+	if cur == enc.buf.Len() {
+		// User-supplied EncodeTime is a no-op. Fall back to nanos since epoch to keep
+		// output JSON valid.
+		enc.AppendInt64(val.UnixNano())
+	}
+}
+
+func (enc *jsonEncoder) AppendUint64(val uint64) {
+	enc.addElementSeparator()
+	enc.buf.AppendUint(val)
+}
+
+func (enc *jsonEncoder) AddComplex64(k string, v complex64) { enc.AddComplex128(k, complex128(v)) }
+func (enc *jsonEncoder) AddFloat32(k string, v float32)     { enc.AddFloat64(k, float64(v)) }
+func (enc *jsonEncoder) AddInt(k string, v int)             { enc.AddInt64(k, int64(v)) }
+func (enc *jsonEncoder) AddInt32(k string, v int32)         { enc.AddInt64(k, int64(v)) }
+func (enc *jsonEncoder) AddInt16(k string, v int16)         { enc.AddInt64(k, int64(v)) }
+func (enc *jsonEncoder) AddInt8(k string, v int8)           { enc.AddInt64(k, int64(v)) }
+func (enc *jsonEncoder) AddUint(k string, v uint)           { enc.AddUint64(k, uint64(v)) }
+func (enc *jsonEncoder) AddUint32(k string, v uint32)       { enc.AddUint64(k, uint64(v)) }
+func (enc *jsonEncoder) AddUint16(k string, v uint16)       { enc.AddUint64(k, uint64(v)) }
+func (enc *jsonEncoder) AddUint8(k string, v uint8)         { enc.AddUint64(k, uint64(v)) }
+func (enc *jsonEncoder) AddUintptr(k string, v uintptr)     { enc.AddUint64(k, uint64(v)) }
+func (enc *jsonEncoder) AppendComplex64(v complex64)        { enc.AppendComplex128(complex128(v)) }
+func (enc *jsonEncoder) AppendFloat64(v float64)            { enc.appendFloat(v, 64) }
+func (enc *jsonEncoder) AppendFloat32(v float32)            { enc.appendFloat(float64(v), 32) }
+func (enc *jsonEncoder) AppendInt(v int)                    { enc.AppendInt64(int64(v)) }
+func (enc *jsonEncoder) AppendInt32(v int32)                { enc.AppendInt64(int64(v)) }
+func (enc *jsonEncoder) AppendInt16(v int16)                { enc.AppendInt64(int64(v)) }
+func (enc *jsonEncoder) AppendInt8(v int8)                  { enc.AppendInt64(int64(v)) }
+func (enc *jsonEncoder) AppendUint(v uint)                  { enc.AppendUint64(uint64(v)) }
+func (enc *jsonEncoder) AppendUint32(v uint32)              { enc.AppendUint64(uint64(v)) }
+func (enc *jsonEncoder) AppendUint16(v uint16)              { enc.AppendUint64(uint64(v)) }
+func (enc *jsonEncoder) AppendUint8(v uint8)                { enc.AppendUint64(uint64(v)) }
+func (enc *jsonEncoder) AppendUintptr(v uintptr)            { enc.AppendUint64(uint64(v)) }
+
+func (enc *jsonEncoder) Clone() Encoder {
+	clone := enc.clone()
+	clone.buf.Write(enc.buf.Bytes())
+	return clone
+}
+
+func (enc *jsonEncoder) clone() *jsonEncoder {
+	clone := getJSONEncoder()
+	clone.EncoderConfig = enc.EncoderConfig
+	clone.spaced = enc.spaced
+	clone.openNamespaces = enc.openNamespaces
+	clone.buf = bufferpool.Get()
+	return clone
+}
+
+func (enc *jsonEncoder) EncodeEntry(ent Entry, fields []Field) (*buffer.Buffer, error) {
+	final := enc.clone()
+	final.buf.AppendByte('{')
+
+	if final.LevelKey != "" {
+		final.addKey(final.LevelKey)
+		cur := final.buf.Len()
+		final.EncodeLevel(ent.Level, final)
+		if cur == final.buf.Len() {
+			// User-supplied EncodeLevel was a no-op. Fall back to strings to keep
+			// output JSON valid.
+			final.AppendString(ent.Level.String())
+		}
+	}
+	if final.TimeKey != "" {
+		final.AddTime(final.TimeKey, ent.Time)
+	}
+	if ent.LoggerName != "" && final.NameKey != "" {
+		final.addKey(final.NameKey)
+		cur := final.buf.Len()
+		nameEncoder := final.EncodeName
+
+		// if no name encoder provided, fall back to FullNameEncoder for backwards
+		// compatibility
+		if nameEncoder == nil {
+			nameEncoder = FullNameEncoder
+		}
+
+		nameEncoder(ent.LoggerName, final)
+		if cur == final.buf.Len() {
+			// User-supplied EncodeName was a no-op. Fall back to strings to
+			// keep output JSON valid.
+			final.AppendString(ent.LoggerName)
+		}
+	}
+	if ent.Caller.Defined && final.CallerKey != "" {
+		final.addKey(final.CallerKey)
+		cur := final.buf.Len()
+		final.EncodeCaller(ent.Caller, final)
+		if cur == final.buf.Len() {
+			// User-supplied EncodeCaller was a no-op. Fall back to strings to
+			// keep output JSON valid.
+			final.AppendString(ent.Caller.String())
+		}
+	}
+	if final.MessageKey != "" {
+		final.addKey(enc.MessageKey)
+		final.AppendString(ent.Message)
+	}
+	if enc.buf.Len() > 0 {
+		final.addElementSeparator()
+		final.buf.Write(enc.buf.Bytes())
+	}
+	addFields(final, fields)
+	final.closeOpenNamespaces()
+	if ent.Stack != "" && final.StacktraceKey != "" {
+		final.AddString(final.StacktraceKey, ent.Stack)
+	}
+	final.buf.AppendByte('}')
+	if final.LineEnding != "" {
+		final.buf.AppendString(final.LineEnding)
+	} else {
+		final.buf.AppendString(DefaultLineEnding)
+	}
+
+	ret := final.buf
+	putJSONEncoder(final)
+	return ret, nil
+}
+
+func (enc *jsonEncoder) truncate() {
+	enc.buf.Reset()
+}
+
+func (enc *jsonEncoder) closeOpenNamespaces() {
+	for i := 0; i < enc.openNamespaces; i++ {
+		enc.buf.AppendByte('}')
+	}
+}
+
+func (enc *jsonEncoder) addKey(key string) {
+	enc.addElementSeparator()
+	enc.buf.AppendByte('"')
+	enc.safeAddString(key)
+	enc.buf.AppendByte('"')
+	enc.buf.AppendByte(':')
+	if enc.spaced {
+		enc.buf.AppendByte(' ')
+	}
+}
+
+func (enc *jsonEncoder) addElementSeparator() {
+	last := enc.buf.Len() - 1
+	if last < 0 {
+		return
+	}
+	switch enc.buf.Bytes()[last] {
+	case '{', '[', ':', ',', ' ':
+		return
+	default:
+		enc.buf.AppendByte(',')
+		if enc.spaced {
+			enc.buf.AppendByte(' ')
+		}
+	}
+}
+
+func (enc *jsonEncoder) appendFloat(val float64, bitSize int) {
+	enc.addElementSeparator()
+	switch {
+	case math.IsNaN(val):
+		enc.buf.AppendString(`"NaN"`)
+	case math.IsInf(val, 1):
+		enc.buf.AppendString(`"+Inf"`)
+	case math.IsInf(val, -1):
+		enc.buf.AppendString(`"-Inf"`)
+	default:
+		enc.buf.AppendFloat(val, bitSize)
+	}
+}
+
+// safeAddString JSON-escapes a string and appends it to the internal buffer.
+// Unlike the standard library's encoder, it doesn't attempt to protect the
+// user from browser vulnerabilities or JSONP-related problems.
+func (enc *jsonEncoder) safeAddString(s string) {
+	for i := 0; i < len(s); {
+		if enc.tryAddRuneSelf(s[i]) {
+			i++
+			continue
+		}
+		r, size := utf8.DecodeRuneInString(s[i:])
+		if enc.tryAddRuneError(r, size) {
+			i++
+			continue
+		}
+		enc.buf.AppendString(s[i : i+size])
+		i += size
+	}
+}
+
+// safeAddByteString is no-alloc equivalent of safeAddString(string(s)) for s []byte.
+func (enc *jsonEncoder) safeAddByteString(s []byte) {
+	for i := 0; i < len(s); {
+		if enc.tryAddRuneSelf(s[i]) {
+			i++
+			continue
+		}
+		r, size := utf8.DecodeRune(s[i:])
+		if enc.tryAddRuneError(r, size) {
+			i++
+			continue
+		}
+		enc.buf.Write(s[i : i+size])
+		i += size
+	}
+}
+
+// tryAddRuneSelf appends b if it is valid UTF-8 character represented in a single byte.
+func (enc *jsonEncoder) tryAddRuneSelf(b byte) bool {
+	if b >= utf8.RuneSelf {
+		return false
+	}
+	if 0x20 <= b && b != '\\' && b != '"' {
+		enc.buf.AppendByte(b)
+		return true
+	}
+	switch b {
+	case '\\', '"':
+		enc.buf.AppendByte('\\')
+		enc.buf.AppendByte(b)
+	case '\n':
+		enc.buf.AppendByte('\\')
+		enc.buf.AppendByte('n')
+	case '\r':
+		enc.buf.AppendByte('\\')
+		enc.buf.AppendByte('r')
+	case '\t':
+		enc.buf.AppendByte('\\')
+		enc.buf.AppendByte('t')
+	default:
+		// Encode bytes < 0x20, except for the escape sequences above.
+		enc.buf.AppendString(`\u00`)
+		enc.buf.AppendByte(_hex[b>>4])
+		enc.buf.AppendByte(_hex[b&0xF])
+	}
+	return true
+}
+
+func (enc *jsonEncoder) tryAddRuneError(r rune, size int) bool {
+	if r == utf8.RuneError && size == 1 {
+		enc.buf.AppendString(`\ufffd`)
+		return true
+	}
+	return false
+}