解决go1.16移除ioutil包的不兼容影响

client.go

@@ -5,7 +5,6 @@ import (
 	"crypto/md5"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"mime/multipart"
 	"net/http"
 	"net/http/cookiejar"
@@ -224,10 +223,11 @@ func (c *Client) WebWxUploadMedia(file *os.File, request BaseRequest, info Login
 	if err != nil {
 		return nil, err
 	}
-	data, err := ioutil.ReadAll(file)
-	if err != nil {
+	buffer := bytes.Buffer{}
+	if _, err := buffer.ReadFrom(file); err != nil {
 		return nil, err
 	}
+	data := buffer.Bytes()
 	fileMd5 := fmt.Sprintf("%x", md5.Sum(data))
 	cookies := c.Jar.Cookies(path)
 	uploadMediaRequest := map[string]interface{}{

response.go

@@ -1,9 +1,9 @@
 package openwechat
 
 import (
+	"bytes"
 	"encoding/json"
 	"encoding/xml"
-	"io/ioutil"
 	"net/http"
 )
 
@@ -46,5 +46,9 @@ func (r *ReturnResponse) ReadAll() ([]byte, error) {
 	if r.Err() != nil {
 		return nil, r.Err()
 	}
-	return ioutil.ReadAll(r.Body)
+	buffer := bytes.Buffer{}
+	if _, err := buffer.ReadFrom(r.Body); err != nil {
+		return nil, err
+	}
+	return buffer.Bytes(), nil
 }

user.go

@@ -1,8 +1,8 @@
 package openwechat
 
 import (
+	"bytes"
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"os"
 )
@@ -62,11 +62,11 @@ func (u *User) SaveAvatar(filename string) error {
 		return err
 	}
 	defer resp.Body.Close()
-	data, err := ioutil.ReadAll(resp.Body)
-	if err != nil {
+	buffer := bytes.Buffer{}
+	if _, err := buffer.ReadFrom(resp.Body); err != nil {
 		return err
 	}
-	return ioutil.WriteFile(filename, data, os.ModePerm)
+	return os.WriteFile(filename, buffer.Bytes(), os.ModePerm)
 }
 
 func (u *User) sendMsg(msg *SendMessage) error {