diff --git a/duration.go b/duration.go
index 9c332ff..1b8ef04 100644
--- a/duration.go
+++ b/duration.go
@@ -1,17 +1,10 @@
 package getenv
 
 import (
-	"regexp"
 	"time"
-	"strconv"
 	"os"
 )
 
-var (
-	reAlp = regexp.MustCompile(`[a-zA-Z]+`)
-	reNum = regexp.MustCompile(`[0-9]+`)
-)
-
 func Duration(key string, def ...interface{}) time.Duration {
 	var d time.Duration
 	if len(def) != 0 {
@@ -20,7 +13,7 @@ func Duration(key string, def ...interface{}) time.Duration {
 		} else if dr, ok := def[0].(time.Duration); ok {
 			d = dr
 		} else if s, ok := def[0].(string); ok {
-			 d = parseDuration(s)
+			 d, _ = time.ParseDuration(s)
 		}
 	}
 
@@ -28,61 +21,9 @@ func Duration(key string, def ...interface{}) time.Duration {
 	if v == "" {
 		return d
 	}
-	return parseDuration(v)
-}
+	d, _ = time.ParseDuration(v)
 
-func trimArray(a []string) []string {
-	ret := []string{}
-
-	for _, e := range a {
-		if len(e) != 0 {
-			ret = append(ret, e)
-		}
-	}
-	return ret
+	return d
 }
 
-func parseDuration(s string) time.Duration {
-	alp := reAlp.Copy()
-	num := reNum.Copy()
-
-	numNodes := trimArray(alp.Split(s, -1))
-	alpNodes := trimArray(num.Split(s, -1))
-
-	if len(alpNodes) == 0 {
-		if len(numNodes) == 0 {
-			return 0
-		}
-
-		s, err := strconv.Atoi(numNodes[0])
-		if err != nil {
-			return 0
-		}
-		return time.Duration(int64(s)) * time.Second
-	}
-
-	if len(alpNodes) != len(numNodes) {
-		return 0
-	}
-
-	var ret time.Duration
-	for i, n := range numNodes {
-		t, err := strconv.Atoi(n)
-		if err != nil {
-			return 0
-		}
-		d := time.Duration(int64(t))
-		switch alpNodes[i] {
-		case "h":
-			ret += d * time.Hour
-		case "m":
-			ret += d * time.Minute
-		case "s":
-			ret += d * time.Second
-		default:
-			return 0
-		}
-	}
-	return ret
-}
 
diff --git a/duration_test.go b/duration_test.go
index 7bc3847..df81c60 100644
--- a/duration_test.go
+++ b/duration_test.go
@@ -6,28 +6,6 @@ import (
 	"os"
 )
 
-func TestParseDuration(t *testing.T) {
-	tests := []struct {
-		input string
-		want time.Duration
-	}{
-		{"1h0m0s", 1*time.Hour},
-		{"1h30m20s", 1*time.Hour + 30*time.Minute + 20*time.Second},
-		{"60", 60*time.Second},
-		{"", 0},
-		{"a", 0},
-		{"00af00", 0},
-		{"0h30m", 30*time.Minute},
-		{"20s", 20*time.Second},
-	}
-
-	for _, test := range tests {
-		if test.want != parseDuration(test.input) {
-			t.Fatalf("want %v, but %v:", test.want, parseDuration(test.input))
-		}
-	}
-}
-
 func TestDuration(t *testing.T) {
 	tests := []struct {
 		input string