allow users to provide their custom httptrace.ClientTrace (#1857)

providing custom httptrace allows users to debug low
level details such as dial, dns and connection errors
more granularly.

Author: harshavardhana

api.go

@@ -1,6 +1,6 @@
 /*
  * MinIO Go Library for Amazon S3 Compatible Cloud Storage
- * Copyright 2015-2018 MinIO, Inc.
+ * Copyright 2015-2023 MinIO, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,6 +29,7 @@ import (
 	"net"
 	"net/http"
 	"net/http/cookiejar"
+	"net/http/httptrace"
 	"net/http/httputil"
 	"net/url"
 	"os"
@@ -69,6 +70,7 @@ type Client struct {
 
 	// Needs allocation.
 	httpClient     *http.Client
+	httpTrace      *httptrace.ClientTrace
 	bucketLocCache *bucketLocationCache
 
 	// Advanced functionality.
@@ -103,6 +105,7 @@ type Options struct {
 	Creds        *credentials.Credentials
 	Secure       bool
 	Transport    http.RoundTripper
+	Trace        *httptrace.ClientTrace
 	Region       string
 	BucketLookup BucketLookupType
 
@@ -229,6 +232,8 @@ func privateNew(endpoint string, opts *Options) (*Client, error) {
 		}
 	}
 
+	clnt.httpTrace = opts.Trace
+
 	// Instantiate http client and bucket location cache.
 	clnt.httpClient = &http.Client{
 		Jar:       jar,
@@ -771,6 +776,10 @@ func (c *Client) newRequest(ctx context.Context, method string, metadata request
 		return nil, err
 	}
 
+	if c.httpTrace != nil {
+		ctx = httptrace.WithClientTrace(ctx, c.httpTrace)
+	}
+
 	// Initialize a new HTTP request for the method.
 	req, err = http.NewRequestWithContext(ctx, method, targetURL.String(), nil)
 	if err != nil {