Add go functions resources (#1602)

* Update 108-functions.md

* Update content/roadmaps/109-golang/content/100-go-basics/108-functions.md

Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com>

content/roadmaps/109-golang/content/100-go-basics/108-functions.md

@@ -1 +1,12 @@
-# Functions
+# Functions
+
+Discover how functions work in Go, the list of resources below will cover :
+
+ - How to define and call functions in Go?
+ - Named returns in Go?
+ - Handle multiple return types.
+ - Different types of functions in Go.
+ 
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://gobyexample.com/functions'>Go by Example: Functions</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.golangprograms.com/go-language/functions.html'>Functions in go</BadgeLink>