The slice type is an abstraction built on top of Go’s array type

Slices Are Like References to Arrays

A slice does not store any data (except the slice header, where the len, cap and ZerothElement is stored), it just describes a section of an underlying array.
Changing the elements of a slice modifies the corresponding elements of its underlying array.
Other slices that share the same underlying array will see those changes.

len() And cap()

A slice has both a length and a capacity.
The length of a slice is the number of elements it contains.
The capacity of a slice is the number of elements in the underlying array, counting from the first element in the slice.
The length and capacity of a slice s can be obtained using the expressions len(s) and cap(s).
You can extend a slice’s length by re-slicing it, provided it has sufficient capacity.

Creating a Slice with Make

Slices can be created with the built-in make function; this is how you create dynamically-sized arrays.
The make function allocates a zeroed array and returns a slice that refers to that array:

sz := 5
a := make([]int, sz)  // len(a)=5

To specify a capacity, pass a third argument to make:

b := make([]int, 0, 5) // len(b)=0, cap(b)=5
b = b[:cap(b)] // len(b)=5, cap(b)=5
b = b[1:]      // len(b)=4, cap(b)=4