05 - for
06 - if-else
07 - switch
08 - arrays
09 - slices
10 - maps
11 - range
12 - functions
13 - multiple return values
14 - variadic functions
15 - closures
16 - recursion
17 - pointers
Name all main files as main.go
18 - structs
19 - methods
20 - interfaces
21 - errors
22 - goroutines
23 - channels