THRIFT-4908: remove reader&writer in Golang's TBinaryProtocol

Client: go

This closes #1831.
diff --git a/lib/go/thrift/binary_protocol.go b/lib/go/thrift/binary_protocol.go
index 1f90bf4..93ae898 100644
--- a/lib/go/thrift/binary_protocol.go
+++ b/lib/go/thrift/binary_protocol.go
@@ -32,8 +32,6 @@
 type TBinaryProtocol struct {
 	trans         TRichTransport
 	origTransport TTransport
-	reader        io.Reader
-	writer        io.Writer
 	strictRead    bool
 	strictWrite   bool
 	buffer        [64]byte
@@ -55,8 +53,6 @@
 	} else {
 		p.trans = NewTRichTransport(t)
 	}
-	p.reader = p.trans
-	p.writer = p.trans
 	return p
 }
 
@@ -192,21 +188,21 @@
 func (p *TBinaryProtocol) WriteI16(value int16) error {
 	v := p.buffer[0:2]
 	binary.BigEndian.PutUint16(v, uint16(value))
-	_, e := p.writer.Write(v)
+	_, e := p.trans.Write(v)
 	return NewTProtocolException(e)
 }
 
 func (p *TBinaryProtocol) WriteI32(value int32) error {
 	v := p.buffer[0:4]
 	binary.BigEndian.PutUint32(v, uint32(value))
-	_, e := p.writer.Write(v)
+	_, e := p.trans.Write(v)
 	return NewTProtocolException(e)
 }
 
 func (p *TBinaryProtocol) WriteI64(value int64) error {
 	v := p.buffer[0:8]
 	binary.BigEndian.PutUint64(v, uint64(value))
-	_, err := p.writer.Write(v)
+	_, err := p.trans.Write(v)
 	return NewTProtocolException(err)
 }
 
@@ -228,7 +224,7 @@
 	if e != nil {
 		return e
 	}
-	_, err := p.writer.Write(value)
+	_, err := p.trans.Write(value)
 	return NewTProtocolException(err)
 }
 
@@ -468,7 +464,7 @@
 }
 
 func (p *TBinaryProtocol) readAll(buf []byte) error {
-	_, err := io.ReadFull(p.reader, buf)
+	_, err := io.ReadFull(p.trans, buf)
 	return NewTProtocolException(err)
 }