Use a type conversion

Two struct types with identical fields can be converted between each
other. In older versions of Go, the fields had to have identical
struct tags. Since Go 1.8, however, struct tags are ignored during
conversions. It is thus not necessary to manually copy every field
individually.

**Before:**

```
var x T1
y := T2{
  Field1: x.Field1,
  Field2: x.Field2,
}
```

**After:**

```
var x T1
y := T2(x)
```
