struct literal in Go

You can list just a subset of fields by using the Name: syntax. (And the order of named fields is irrelevant.)
The special prefix & returns a pointer to the struct value. 
```
type Vertex struct {
	X, Y int
}

var (
	v1 = Vertex{1, 2}  // has type Vertex
	v2 = Vertex{X: 1}  // Y:0 is implicit
	v3 = Vertex{}      // X:0 and Y:0
	p  = &Vertex{1, 2} // has type *Vertex
)
```