Code Review: Function values and closures

If multiple functions with the same signature are used for similar purposes and assigned to variables, define a function type and use it when declaring the function variables. This clarifies the relationship between the functions and documents their purpose.

Take care when using package-level function variables. Unlike function declarations, they are mutable, which means their functionality can be changed at runtime.

If you have a helper function that’s only used within a single function, consider using a closure for the helper function.

Use function parameters to “plug in” logic to a larger algorithm, such as to specify the sort order when sorting a slice.

Default to using cmp.Compare and cmp.Or when writing comparator functions.