fix: test timeout on slow machines (#340)

Fix test timeout on slow machines by extend testing timeout
to 20 secs.

Fixes: #337

Signed-off-by: Jongmin Kim <jmkim@pukyong.ac.kr>

testing_test.go

@@ -11,7 +11,7 @@ import (
 
 func tt(t *testing.T, arguments ...func()) {
 	halt := errors.New("A test was taking too long")
-	timer := time.AfterFunc(2*time.Second, func() {
+	timer := time.AfterFunc(20*time.Second, func() {
 		panic(halt)
 	})
 	defer func() {