Prefer http.Header over map[string]string to allow for multi-valued headers

api/api.go

@@ -156,7 +156,7 @@ type Config struct {
 	// TLSConfig is ignored if HttpClient is set.
 	TLSConfig *TLSConfig
 
-	Headers map[string]string
+	Headers http.Header
 }
 
 // ClientConfig copies the configuration with a new client address, region, and
@@ -676,9 +676,7 @@ func (c *Client) newRequest(method, path string) (*request, error) {
 		}
 	}
 
-	for key, value := range c.config.Headers {
-		r.header.Set(key, value)
-	}
+	r.header = c.config.Headers
 
 	return r, nil
 }

api/api_test.go

@@ -344,8 +344,8 @@ func TestParseWriteMeta(t *testing.T) {
 func TestClientHeader(t *testing.T) {
 	t.Parallel()
 	c, s := makeClient(t, func(c *Config) {
-		c.Headers = map[string]string{
-			"Hello": "World",
+		c.Headers = http.Header{
+			"Hello": []string{"World"},
 		}
 	}, nil)
 	defer s.Stop()