packages are used to group to related go files together
each go file starts with package keyword
main() function should be present in main package
//syntax for declaring a function in go
func func_name(params) return_type {
}
It needs to be in a file with a name like xxx_test.go
The test function must start with the word Test
The test function takes one argument only t *testing.T
In order to use the *testing.T type, you need to import "testing", like we did with fmt in the other file
t.Run is used to run multiple tests under a single test function
var_name := value
it is a short hand for var var_name = value
some more ways of declaring a variable
var var_name data_type