Go is a statically typed language, meaning you generally have to declare the type of the variables you are using.
// Basic variable declaration. Declares a variable of type specified on the right.
// The variable is initialized to the zero value of the respective type.
var x int
var s string
var p Person // Assuming type Person struct {}
// Assignment of a value to a variable
x = 3
// Short declaration using := infers the type
y := 4
u := int64(100) // declare variable of type int64 and init with 100
var u2 int64 = 100 // declare variable of type int64 and init with 100