add concurrency for client's HostClient map (#1550)

* add the functions to get host clients

* add concurrency for client's HostClient map

* delete test code

* add lock in once block

---------

Co-authored-by: wangzhengkai.wzk <wangzhengkai.wzk@alibaba-inc.com>

client.go

@@ -303,7 +303,8 @@ type Client struct {
 	// ConfigureClient configures the fasthttp.HostClient.
 	ConfigureClient func(hc *HostClient) error
 
-	mLock      sync.Mutex
+	mLock      sync.RWMutex
+	mOnce      sync.Once
 	m          map[string]*HostClient
 	ms         map[string]*HostClient
 	readerPool sync.Pool
@@ -485,68 +486,71 @@ func (c *Client) Do(req *Request, resp *Response) error {
 		return fmt.Errorf("unsupported protocol %q. http and https are supported", uri.Scheme())
 	}
 
+	c.mOnce.Do(func() {
+		c.mLock.Lock()
+		c.m = make(map[string]*HostClient)
+		c.ms = make(map[string]*HostClient)
+		c.mLock.Unlock()
+	})
+
 	startCleaner := false
 
-	c.mLock.Lock()
+	c.mLock.RLock()
 	m := c.m
 	if isTLS {
 		m = c.ms
 	}
-	if m == nil {
-		m = make(map[string]*HostClient)
-		if isTLS {
-			c.ms = m
-		} else {
-			c.m = m
-		}
-	}
 	hc := m[string(host)]
+	c.mLock.RUnlock()
 	if hc == nil {
-		hc = &HostClient{
-			Addr:                          AddMissingPort(string(host), isTLS),
-			Name:                          c.Name,
-			NoDefaultUserAgentHeader:      c.NoDefaultUserAgentHeader,
-			Dial:                          c.Dial,
-			DialDualStack:                 c.DialDualStack,
-			IsTLS:                         isTLS,
-			TLSConfig:                     c.TLSConfig,
-			MaxConns:                      c.MaxConnsPerHost,
-			MaxIdleConnDuration:           c.MaxIdleConnDuration,
-			MaxConnDuration:               c.MaxConnDuration,
-			MaxIdemponentCallAttempts:     c.MaxIdemponentCallAttempts,
-			ReadBufferSize:                c.ReadBufferSize,
-			WriteBufferSize:               c.WriteBufferSize,
-			ReadTimeout:                   c.ReadTimeout,
-			WriteTimeout:                  c.WriteTimeout,
-			MaxResponseBodySize:           c.MaxResponseBodySize,
-			DisableHeaderNamesNormalizing: c.DisableHeaderNamesNormalizing,
-			DisablePathNormalizing:        c.DisablePathNormalizing,
-			MaxConnWaitTimeout:            c.MaxConnWaitTimeout,
-			RetryIf:                       c.RetryIf,
-			ConnPoolStrategy:              c.ConnPoolStrategy,
-			StreamResponseBody:            c.StreamResponseBody,
-			clientReaderPool:              &c.readerPool,
-			clientWriterPool:              &c.writerPool,
-		}
-
-		if c.ConfigureClient != nil {
-			if err := c.ConfigureClient(hc); err != nil {
-				c.mLock.Unlock()
-				return err
+		c.mLock.Lock()
+		hc = m[string(host)]
+		if hc == nil {
+			hc = &HostClient{
+				Addr:                          AddMissingPort(string(host), isTLS),
+				Name:                          c.Name,
+				NoDefaultUserAgentHeader:      c.NoDefaultUserAgentHeader,
+				Dial:                          c.Dial,
+				DialDualStack:                 c.DialDualStack,
+				IsTLS:                         isTLS,
+				TLSConfig:                     c.TLSConfig,
+				MaxConns:                      c.MaxConnsPerHost,
+				MaxIdleConnDuration:           c.MaxIdleConnDuration,
+				MaxConnDuration:               c.MaxConnDuration,
+				MaxIdemponentCallAttempts:     c.MaxIdemponentCallAttempts,
+				ReadBufferSize:                c.ReadBufferSize,
+				WriteBufferSize:               c.WriteBufferSize,
+				ReadTimeout:                   c.ReadTimeout,
+				WriteTimeout:                  c.WriteTimeout,
+				MaxResponseBodySize:           c.MaxResponseBodySize,
+				DisableHeaderNamesNormalizing: c.DisableHeaderNamesNormalizing,
+				DisablePathNormalizing:        c.DisablePathNormalizing,
+				MaxConnWaitTimeout:            c.MaxConnWaitTimeout,
+				RetryIf:                       c.RetryIf,
+				ConnPoolStrategy:              c.ConnPoolStrategy,
+				StreamResponseBody:            c.StreamResponseBody,
+				clientReaderPool:              &c.readerPool,
+				clientWriterPool:              &c.writerPool,
 			}
-		}
 
-		m[string(host)] = hc
-		if len(m) == 1 {
-			startCleaner = true
+			if c.ConfigureClient != nil {
+				if err := c.ConfigureClient(hc); err != nil {
+					c.mLock.Unlock()
+					return err
+				}
+			}
+
+			m[string(host)] = hc
+			if len(m) == 1 {
+				startCleaner = true
+			}
 		}
+		c.mLock.Unlock()
 	}
 
 	atomic.AddInt32(&hc.pendingClientRequests, 1)
 	defer atomic.AddInt32(&hc.pendingClientRequests, -1)
 
-	c.mLock.Unlock()
-
 	if startCleaner {
 		go c.mCleaner(m)
 	}
@@ -559,14 +563,14 @@ func (c *Client) Do(req *Request, resp *Response) error {
 // "keep-alive" state. It does not interrupt any connections currently
 // in use.
 func (c *Client) CloseIdleConnections() {
-	c.mLock.Lock()
+	c.mLock.RLock()
 	for _, v := range c.m {
 		v.CloseIdleConnections()
 	}
 	for _, v := range c.ms {
 		v.CloseIdleConnections()
 	}
-	c.mLock.Unlock()
+	c.mLock.RUnlock()
 }
 
 func (c *Client) mCleaner(m map[string]*HostClient) {