What is package? A package is a collection of source files in the same directory that are compiled together Name convention: packages are given lower case, single-word names there should be no need for underscores or mixedCaps. Example: package mathutils Constants: Constants are immutable Example: const x int64 = 100 const pi = 2.14 Go doesn’t provide a way to specify that a value calculated at runtime. For example, the following code will fail to compile with the error x + y (value of type int) is not constant: Constants can be typed or untyped x := 5 y := 10 const z = x + y // this won't compile!