feat(sdk): support compressed response (#469)

* enable use compression algorithm

* fix ci

* Just enable decode compressed content at ethclient

* fix comments

---------

Co-authored-by: Haichen Shen <shenhaichen@gmail.com>

ethclient/ethclient.go

@@ -54,6 +54,11 @@ func NewClient(c *rpc.Client) *Client {
 	return &Client{c}
 }
 
+// SetHeader expose the function, in able to set http header.
+func (ec *Client) SetHeader(key, value string) {
+	ec.c.SetHeader(key, value)
+}
+
 func (ec *Client) Close() {
 	ec.c.Close()
 }

rpc/http.go

@@ -18,6 +18,8 @@ package rpc
 
 import (
 	"bytes"
+	"compress/gzip"
+	"compress/zlib"
 	"context"
 	"encoding/json"
 	"errors"
@@ -27,6 +29,7 @@ import (
 	"mime"
 	"net/http"
 	"net/url"
+	"strings"
 	"sync"
 	"time"
 )
@@ -198,7 +201,9 @@ func (hc *httpConn) doRequest(ctx context.Context, msg interface{}) (io.ReadClos
 			Body:       body,
 		}
 	}
-	return resp.Body, nil
+
+	// if encoding is set use it.
+	return newDecodeCompression(resp.Header.Get("Content-Encoding"), resp.Body)
 }
 
 // httpServerConn turns a HTTP connection into a Conn.
@@ -208,6 +213,28 @@ type httpServerConn struct {
 	r *http.Request
 }
 
+func newDecodeCompression(decoding string, rc io.ReadCloser) (io.ReadCloser, error) {
+	tps := strings.Split(strings.TrimSpace(strings.ToLower(decoding)), ",")
+	var res io.ReadCloser
+	switch tps[0] {
+	case "gzip":
+		gz, err := gzip.NewReader(rc)
+		if err != nil {
+			return nil, err
+		}
+		res = gz
+	case "deflate":
+		zl, err := zlib.NewReader(rc)
+		if err != nil {
+			return nil, err
+		}
+		res = zl
+	default:
+		res = rc
+	}
+	return res, nil
+}
+
 func newHTTPServerConn(r *http.Request, w http.ResponseWriter) ServerCodec {
 	body := io.LimitReader(r.Body, maxRequestContentLength)
 	conn := &httpServerConn{Reader: body, Writer: w, r: r}