refactor: first four section, organize cont.

02-write-your-first-program/exercises/02-print-gopath/exercise.md

@@ -0,0 +1,8 @@
+// ---------------------------------------------------------
+// EXERCISE: Print GOPATH
+//
+//  Print your GOPATH using `go env` tool
+//
+// EXPECTED OUTPUT
+//  The physical folder path that is referenced by $GOPATH
+// ---------------------------------------------------------

02-write-your-first-program/exercises/02-print-gopath/solution/solution.md

@@ -0,0 +1,3 @@
+You should type this:
+
+go env GOPATH