add example

Author: Alexandru Efimov

example/main.go

@@ -0,0 +1,32 @@
+package main
+
+import "github.com/efimovalex/stackerr"
+import "fmt"
+
+func f1() *stackerr.Err {
+	err := stackerr.Error("message")
+	return err.Stack()
+}
+
+func f2() *stackerr.Err {
+	err := f1()
+	return err.Stack()
+}
+
+type t1 struct{}
+
+func (t *t1) f3() *stackerr.Err {
+	err := f2()
+	return err.Stack()
+}
+
+func main() {
+	ts := t1{}
+	err := ts.f3()
+
+	fmt.Println(err.Sprint())
+
+	fmt.Println(err.Error())
+
+	err.Log()
+}