Merge pull request #15 from ieee0824/check

add Exists function

Author: ieee0824

check.go

@@ -0,0 +1,9 @@
+package getenv
+
+import "os"
+
+func Exists(key string) bool {
+	_, ok := os.LookupEnv(key)
+
+	return ok
+}

check_test.go

@@ -0,0 +1,36 @@
+package getenv
+
+import "testing"
+
+func TestExists(t *testing.T) {
+	tests := []struct {
+		name string
+		key  string
+		val  string
+		want bool
+	}{
+		{
+			name: "key not exists",
+			want: false,
+		},
+		{
+			name: "key exists",
+			key:  "SOME_ENV",
+			val:  "some_value",
+			want: true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if test.val != "" {
+				t.Setenv(test.key, test.val)
+			}
+
+			got := Exists(test.key)
+			if got != test.want {
+				t.Fatalf("name %s, want %v, but %v:", test.name, test.want, got)
+			}
+		})
+	}
+}