feat: adding example of overwriting User-Agent header

Author: vlastahajek

example_ua_set_test.go

@@ -0,0 +1,54 @@
+// Copyright 2022 InfluxData, Inc. All rights reserved.
+// Use of this source code is governed by MIT
+// license that can be found in the LICENSE file.
+
+package influxdb2_test
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"github.com/influxdata/influxdb-client-go/v2"
+	ihttp "github.com/influxdata/influxdb-client-go/v2/api/http"
+)
+
+// UserAgentSetter is the implementation of Doer interface for setting User-Agent header
+type UserAgentSetter struct {
+	UserAgent   string
+	RequestDoer ihttp.Doer
+}
+
+// Do fulfills the Doer interface
+func (u *UserAgentSetter) Do(req *http.Request) (*http.Response, error) {
+	// Set User-Agent header to request
+	req.Header.Set("User-Agent", u.UserAgent)
+	// Call original Doer to proceed with request
+	return u.RequestDoer.Do(req)
+}
+
+func ExampleClient_customUserAgentHeader() {
+	// Set custom Doer to HTTPOptions
+	opts := influxdb2.DefaultOptions()
+	opts.HTTPOptions().SetHTTPDoer(&UserAgentSetter{
+		UserAgent:   "NetMonitor/1.1",
+		RequestDoer: http.DefaultClient,
+	})
+
+	//Create client with customized options
+	client := influxdb2.NewClientWithOptions("http://localhost:8086", "my-token", opts)
+
+	// Always close client at the end
+	defer client.Close()
+
+	// Issue a call with custom User-Agent header
+	resp, err := client.Ping(context.Background())
+	if err != nil {
+		panic(err)
+	}
+	if resp {
+		fmt.Println("Server is up")
+	} else {
+		fmt.Println("Server is down")
+	}
+}