func append(slice []Type, elems ...Type) []Type
The append built-in function appends elements to the end of a slice.
If it has sufficient capacity, the destination is resliced to accommodate
the new elements. If it does not, a new underlying array will be allocated.
Append returns the updated slice. It is therefore necessary to store the
result of append, often in the variable holding the slice itself:
slice = append(slice, elem1, elem2)
slice = append(slice, anotherSlice...)
As a special case, it is legal to append a string to a byte slice, like this:
slice = append([]byte("hello "), "world"...)1. https://golang.org/pkg/builtin/#append