diff --git a/vendor/google.golang.org/protobuf/internal/encoding/json/decode.go b/vendor/google.golang.org/protobuf/internal/encoding/json/decode.go
new file mode 100644
index 0000000..b13fd29
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/internal/encoding/json/decode.go
@@ -0,0 +1,340 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"regexp"
+	"unicode/utf8"
+
+	"google.golang.org/protobuf/internal/errors"
+)
+
+// call specifies which Decoder method was invoked.
+type call uint8
+
+const (
+	readCall call = iota
+	peekCall
+)
+
+const unexpectedFmt = "unexpected token %s"
+
+// ErrUnexpectedEOF means that EOF was encountered in the middle of the input.
+var ErrUnexpectedEOF = errors.New("%v", io.ErrUnexpectedEOF)
+
+// Decoder is a token-based JSON decoder.
+type Decoder struct {
+	// lastCall is last method called, either readCall or peekCall.
+	// Initial value is readCall.
+	lastCall call
+
+	// lastToken contains the last read token.
+	lastToken Token
+
+	// lastErr contains the last read error.
+	lastErr error
+
+	// openStack is a stack containing ObjectOpen and ArrayOpen values. The
+	// top of stack represents the object or the array the current value is
+	// directly located in.
+	openStack []Kind
+
+	// orig is used in reporting line and column.
+	orig []byte
+	// in contains the unconsumed input.
+	in []byte
+}
+
+// NewDecoder returns a Decoder to read the given []byte.
+func NewDecoder(b []byte) *Decoder {
+	return &Decoder{orig: b, in: b}
+}
+
+// Peek looks ahead and returns the next token kind without advancing a read.
+func (d *Decoder) Peek() (Token, error) {
+	defer func() { d.lastCall = peekCall }()
+	if d.lastCall == readCall {
+		d.lastToken, d.lastErr = d.Read()
+	}
+	return d.lastToken, d.lastErr
+}
+
+// Read returns the next JSON token.
+// It will return an error if there is no valid token.
+func (d *Decoder) Read() (Token, error) {
+	const scalar = Null | Bool | Number | String
+
+	defer func() { d.lastCall = readCall }()
+	if d.lastCall == peekCall {
+		return d.lastToken, d.lastErr
+	}
+
+	tok, err := d.parseNext()
+	if err != nil {
+		return Token{}, err
+	}
+
+	switch tok.kind {
+	case EOF:
+		if len(d.openStack) != 0 ||
+			d.lastToken.kind&scalar|ObjectClose|ArrayClose == 0 {
+			return Token{}, ErrUnexpectedEOF
+		}
+
+	case Null:
+		if !d.isValueNext() {
+			return Token{}, d.newSyntaxError(tok.pos, unexpectedFmt, tok.RawString())
+		}
+
+	case Bool, Number:
+		if !d.isValueNext() {
+			return Token{}, d.newSyntaxError(tok.pos, unexpectedFmt, tok.RawString())
+		}
+
+	case String:
+		if d.isValueNext() {
+			break
+		}
+		// This string token should only be for a field name.
+		if d.lastToken.kind&(ObjectOpen|comma) == 0 {
+			return Token{}, d.newSyntaxError(tok.pos, unexpectedFmt, tok.RawString())
+		}
+		if len(d.in) == 0 {
+			return Token{}, ErrUnexpectedEOF
+		}
+		if c := d.in[0]; c != ':' {
+			return Token{}, d.newSyntaxError(d.currPos(), `unexpected character %s, missing ":" after field name`, string(c))
+		}
+		tok.kind = Name
+		d.consume(1)
+
+	case ObjectOpen, ArrayOpen:
+		if !d.isValueNext() {
+			return Token{}, d.newSyntaxError(tok.pos, unexpectedFmt, tok.RawString())
+		}
+		d.openStack = append(d.openStack, tok.kind)
+
+	case ObjectClose:
+		if len(d.openStack) == 0 ||
+			d.lastToken.kind == comma ||
+			d.openStack[len(d.openStack)-1] != ObjectOpen {
+			return Token{}, d.newSyntaxError(tok.pos, unexpectedFmt, tok.RawString())
+		}
+		d.openStack = d.openStack[:len(d.openStack)-1]
+
+	case ArrayClose:
+		if len(d.openStack) == 0 ||
+			d.lastToken.kind == comma ||
+			d.openStack[len(d.openStack)-1] != ArrayOpen {
+			return Token{}, d.newSyntaxError(tok.pos, unexpectedFmt, tok.RawString())
+		}
+		d.openStack = d.openStack[:len(d.openStack)-1]
+
+	case comma:
+		if len(d.openStack) == 0 ||
+			d.lastToken.kind&(scalar|ObjectClose|ArrayClose) == 0 {
+			return Token{}, d.newSyntaxError(tok.pos, unexpectedFmt, tok.RawString())
+		}
+	}
+
+	// Update d.lastToken only after validating token to be in the right sequence.
+	d.lastToken = tok
+
+	if d.lastToken.kind == comma {
+		return d.Read()
+	}
+	return tok, nil
+}
+
+// Any sequence that looks like a non-delimiter (for error reporting).
+var errRegexp = regexp.MustCompile(`^([-+._a-zA-Z0-9]{1,32}|.)`)
+
+// parseNext parses for the next JSON token. It returns a Token object for
+// different types, except for Name. It does not handle whether the next token
+// is in a valid sequence or not.
+func (d *Decoder) parseNext() (Token, error) {
+	// Trim leading spaces.
+	d.consume(0)
+
+	in := d.in
+	if len(in) == 0 {
+		return d.consumeToken(EOF, 0), nil
+	}
+
+	switch in[0] {
+	case 'n':
+		if n := matchWithDelim("null", in); n != 0 {
+			return d.consumeToken(Null, n), nil
+		}
+
+	case 't':
+		if n := matchWithDelim("true", in); n != 0 {
+			return d.consumeBoolToken(true, n), nil
+		}
+
+	case 'f':
+		if n := matchWithDelim("false", in); n != 0 {
+			return d.consumeBoolToken(false, n), nil
+		}
+
+	case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+		if n, ok := parseNumber(in); ok {
+			return d.consumeToken(Number, n), nil
+		}
+
+	case '"':
+		s, n, err := d.parseString(in)
+		if err != nil {
+			return Token{}, err
+		}
+		return d.consumeStringToken(s, n), nil
+
+	case '{':
+		return d.consumeToken(ObjectOpen, 1), nil
+
+	case '}':
+		return d.consumeToken(ObjectClose, 1), nil
+
+	case '[':
+		return d.consumeToken(ArrayOpen, 1), nil
+
+	case ']':
+		return d.consumeToken(ArrayClose, 1), nil
+
+	case ',':
+		return d.consumeToken(comma, 1), nil
+	}
+	return Token{}, d.newSyntaxError(d.currPos(), "invalid value %s", errRegexp.Find(in))
+}
+
+// newSyntaxError returns an error with line and column information useful for
+// syntax errors.
+func (d *Decoder) newSyntaxError(pos int, f string, x ...interface{}) error {
+	e := errors.New(f, x...)
+	line, column := d.Position(pos)
+	return errors.New("syntax error (line %d:%d): %v", line, column, e)
+}
+
+// Position returns line and column number of given index of the original input.
+// It will panic if index is out of range.
+func (d *Decoder) Position(idx int) (line int, column int) {
+	b := d.orig[:idx]
+	line = bytes.Count(b, []byte("\n")) + 1
+	if i := bytes.LastIndexByte(b, '\n'); i >= 0 {
+		b = b[i+1:]
+	}
+	column = utf8.RuneCount(b) + 1 // ignore multi-rune characters
+	return line, column
+}
+
+// currPos returns the current index position of d.in from d.orig.
+func (d *Decoder) currPos() int {
+	return len(d.orig) - len(d.in)
+}
+
+// matchWithDelim matches s with the input b and verifies that the match
+// terminates with a delimiter of some form (e.g., r"[^-+_.a-zA-Z0-9]").
+// As a special case, EOF is considered a delimiter. It returns the length of s
+// if there is a match, else 0.
+func matchWithDelim(s string, b []byte) int {
+	if !bytes.HasPrefix(b, []byte(s)) {
+		return 0
+	}
+
+	n := len(s)
+	if n < len(b) && isNotDelim(b[n]) {
+		return 0
+	}
+	return n
+}
+
+// isNotDelim returns true if given byte is a not delimiter character.
+func isNotDelim(c byte) bool {
+	return (c == '-' || c == '+' || c == '.' || c == '_' ||
+		('a' <= c && c <= 'z') ||
+		('A' <= c && c <= 'Z') ||
+		('0' <= c && c <= '9'))
+}
+
+// consume consumes n bytes of input and any subsequent whitespace.
+func (d *Decoder) consume(n int) {
+	d.in = d.in[n:]
+	for len(d.in) > 0 {
+		switch d.in[0] {
+		case ' ', '\n', '\r', '\t':
+			d.in = d.in[1:]
+		default:
+			return
+		}
+	}
+}
+
+// isValueNext returns true if next type should be a JSON value: Null,
+// Number, String or Bool.
+func (d *Decoder) isValueNext() bool {
+	if len(d.openStack) == 0 {
+		return d.lastToken.kind == 0
+	}
+
+	start := d.openStack[len(d.openStack)-1]
+	switch start {
+	case ObjectOpen:
+		return d.lastToken.kind&Name != 0
+	case ArrayOpen:
+		return d.lastToken.kind&(ArrayOpen|comma) != 0
+	}
+	panic(fmt.Sprintf(
+		"unreachable logic in Decoder.isValueNext, lastToken.kind: %v, openStack: %v",
+		d.lastToken.kind, start))
+}
+
+// consumeToken constructs a Token for given Kind with raw value derived from
+// current d.in and given size, and consumes the given size-lenght of it.
+func (d *Decoder) consumeToken(kind Kind, size int) Token {
+	tok := Token{
+		kind: kind,
+		raw:  d.in[:size],
+		pos:  len(d.orig) - len(d.in),
+	}
+	d.consume(size)
+	return tok
+}
+
+// consumeBoolToken constructs a Token for a Bool kind with raw value derived from
+// current d.in and given size.
+func (d *Decoder) consumeBoolToken(b bool, size int) Token {
+	tok := Token{
+		kind: Bool,
+		raw:  d.in[:size],
+		pos:  len(d.orig) - len(d.in),
+		boo:  b,
+	}
+	d.consume(size)
+	return tok
+}
+
+// consumeStringToken constructs a Token for a String kind with raw value derived
+// from current d.in and given size.
+func (d *Decoder) consumeStringToken(s string, size int) Token {
+	tok := Token{
+		kind: String,
+		raw:  d.in[:size],
+		pos:  len(d.orig) - len(d.in),
+		str:  s,
+	}
+	d.consume(size)
+	return tok
+}
+
+// Clone returns a copy of the Decoder for use in reading ahead the next JSON
+// object, array or other values without affecting current Decoder.
+func (d *Decoder) Clone() *Decoder {
+	ret := *d
+	ret.openStack = append([]Kind(nil), ret.openStack...)
+	return &ret
+}