easy convert

there are two structs with the same filed

```go
type AA struct {
	Name string
	Addr string
}

type BB struct {
	Name string
	Addr string
}
```

init A with B data we should init like follow:

```go
aa := A{Name: b.Name, Addr: b.Addr}
```

sometimes the struct has more fields, this init logic will be too large and cannot be readable.