Add must

Author: mattn

must/go.mod

@@ -0,0 +1,3 @@
+module github.com/mattn/go-generics-example/must
+
+go 1.18

must/main.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"os"
+)
+
+func Must[T any](v T, err error) T {
+	if err != nil {
+		panic(err.Error())
+	}
+	return v
+}
+
+func Must2[T1 any, T2 any](v1 T1, v2 T2, err error) (T1, T2) {
+	if err != nil {
+		panic(err.Error())
+	}
+	return v1, v2
+}
+
+func Must3[T1 any, T2 any, T3 any](v1 T1, v2 T2, v3 T3, err error) (T1, T2, T3) {
+	if err != nil {
+		panic(err.Error())
+	}
+	return v1, v2, v3
+}
+
+func main() {
+	f := Must(os.Create("test.txt"))
+	defer os.Remove("test.txt")
+	defer f.Close()
+	f.Write([]byte("hello"))
+}