Add experimental support for HTTP/3 (#8)

* Wait for service in integration tests instead of watching for a string

* Add http3 experimental support

internal/setting/app.go

@@ -29,6 +29,7 @@ type settings struct {
 	TrustedHeader       string
 	TrustedPortHeader   string
 	EnableSecureHeaders bool
+	EnableHTTP3         bool
 	Server              serverSettings
 	version             bool
 }
@@ -89,6 +90,12 @@ func Setup(args []string) (output string, err error) {
 		false,
 		"Add sane security-related headers to every response",
 	)
+	flags.BoolVar(
+		&App.EnableHTTP3,
+		"enable-http3",
+		false,
+		"Enable HTTP/3 protocol. HTTP/3 requires --tls-bind set, as HTTP/3 starts as a TLS connection that then gets upgraded to UDP. The UDP port is the same as the one used for the TLS server.",
+	)
 
 	err = flags.Parse(args)
 	if err != nil {
@@ -111,6 +118,10 @@ func Setup(args []string) (output string, err error) {
 		return "", fmt.Errorf("in order to use TLS, the -tls-crt and -tls-key flags are mandatory")
 	}
 
+	if App.EnableHTTP3 && App.TLSAddress == "" {
+		return "", fmt.Errorf("in order to use HTTP3, the -tls-bind is mandatory")
+	}
+
 	if App.TemplatePath != "" {
 		info, err := os.Stat(App.TemplatePath)
 		if os.IsNotExist(err) {

internal/setting/app_test.go

@@ -41,6 +41,11 @@ func TestParseMandatoryFlags(t *testing.T) {
 				"-tls-key", "/key-path",
 			},
 		},
+		{
+			[]string{
+				"-geoip2-city", "/city-path", "-geoip2-asn", "/asn-path", "-enable-http3",
+			},
+		},
 		{
 			[]string{
 				"-geoip2-city", "/city-path", "-geoip2-asn", "/asn-path", "-bind", ":8000",