implement WithHeader function, for custom headers to be set in each r…

…equest

httpclient.go

@@ -52,6 +52,9 @@ type Client struct {
 	username string
 	password string
 
+	// custom http header
+	header http.Header
+
 	Marshaler   MarshalerFunc
 	Unmarshaler UnmarshalerFunc
 
@@ -187,6 +190,14 @@ func WithContentType(ct string) Opt {
 	}
 }
 
+// WithHeader is a client option for setting custom http header(s) for each request
+func WithHeader(header http.Header) Opt {
+	return func(c *Client) error {
+		c.header = header
+		return nil
+	}
+}
+
 // NewRequest creates an API request. A relative URL can be provided in urlStr, which will be resolved to the
 // BaseURL of the Client. Relative URLs should always be specified without a preceding slash. If specified, the
 // value pointed to by body will be encoded and included in as the request body.
@@ -217,6 +228,9 @@ func (c *Client) NewRequest(method, urlStr string, body interface{}) (*http.Requ
 		req.SetBasicAuth(c.username, c.password)
 	}
 
+	if c.header != nil {
+		req.Header = c.header
+	}
 	req.Header.Add("Content-Type", contentType)
 	req.Header.Add("Accept", contentType)
 

httpclient_test.go

@@ -108,6 +108,19 @@ func TestClient(t *testing.T) {
 		assert.Equal(t, password, c.password)
 	})
 
+	t.Run("new client with headers", func(t *testing.T) {
+		customHeader := http.Header{
+			"X-Requested-By": []string{"test"},
+		}
+		c, err := New(baseurl, WithHeader(customHeader))
+		assert.Nil(t, err)
+		assert.NotNil(t, c)
+
+		req, err := c.NewRequest(http.MethodGet, "/test", nil)
+		assert.Nil(t, err)
+		assert.Equal(t, req.Header, customHeader)
+	})
+
 	t.Run("new client valid baseurl valid HTTP client", func(t *testing.T) {
 		httpC := &http.Client{}
 		c, err := New(baseurl, WithHTTPClient(httpC))