Added functions and fixed a typo in Loops.md

Added functions in golang.

Fixed the typo in for-range loop in Loops.md. Changed "for index, value
in range" to "for index, value := range"

Author: shrn01

Diff for: tutorials/learn-golang.org/en/Functions.md

@@ -0,0 +1,111 @@
+Tutorial
+--------
+Functions provide a way to divide your code into logical blocks and reuse them minimising the time and effort and improve the managability of the code. 
+
+## Functions in Go
+
+Functions in golang are defined using the `func` keyword. 
+
+The syntax to define a function in go
+
+    func <name of the function> (<inputs to the function>) (<datatypes of return values from the function>) {
+        // your code here
+    }
+
+Let's write a add function using this syntax
+
+    func add (a int, b int) int {
+        return a + b
+    }
+
+## How to call a function in your code
+
+Calling a function is as easy as writing the function name and giving it the arguments. Now for an example let's call our add function in the main method.
+
+    package main
+
+	import "fmt"
+
+	func main() {
+		sum := add(3, 5)
+
+        fmt.Println(sum)        // prints 8
+	}
+
+Go also let's you ignore specific fields in the return values using the `_` variable. 
+
+    package main
+
+	import "fmt"
+
+    func sumAndDiff (a int, b int) (int, int) {
+        return a + b, a - b
+    }
+
+	func main() {
+		sum, _ := sumAndDiff(5, 3)      // the 2nd variable is ignored and not used
+
+        fmt.Println(sum)                // prints 8
+	}
+
+
+We can also add named return values so that we dont need to deliberately return something in the function. But beware, use this only in small functions.
+
+    package main
+
+	import "fmt"
+
+    func add (a int, b int) (sum int) {         // here we are defining the variable name of what we are returning
+        sum = a + b                             // so no need for a return statement, go takes care of it
+    }
+
+	func main() {
+		sum := add(3, 5)
+
+        fmt.Println(sum)                // prints 8
+	}
+
+
+Exercise
+--------
+In this exercise, your will be given a integer slice as a input. Write a function with name `sumAll` that loops through all the numbers in the slice and returns the sum of the numbers. 
+
+Tutorial Code
+-------------
+package main
+
+import "fmt"
+
+// your code here
+
+func main() {
+    list := []int{1, 2, 3, 4, 5, 6}
+
+    fmt.Println(sumAll(list))
+}
+
+Expected Output
+---------------
+21
+
+Solution
+--------
+package main
+
+import "fmt"
+
+func sumAll(list []int) int {
+    sum := 0
+
+    for _, value := range list {
+        sum = sum + value
+    }
+    
+    return sum
+}
+
+func main() {
+    list := []int{1, 2, 3, 4, 5, 6}
+
+    fmt.Println(sumAll(list))
+}

Diff for: tutorials/learn-golang.org/en/Loops.md

@@ -57,14 +57,14 @@ The for-range loop provides us access to the index and value of the elements in
 	func main() {
 		myList := []int{1,2,3}
 
-		for index, value in range myList {
+		for index, value := range myList {
 			fmt.Printf("%d is index, %d is value", index, value)
 		}
 	}
 
 We can ignore one or both the fields in a for-range loop by giving an `_` instead of giving a variable name
 
-		for _, value in range myList {
+		for _, value := range myList {
 			fmt.Println(value)
 		}
 

Diff for: tutorials/learn-golang.org/en/Welcome.md

@@ -16,6 +16,7 @@ learn-golang.org is still under construction - If you wish to contribute tutoria
 - [[Slices]]
 - [[If-Else]]
 - [[Loops]]
+- [[Functions]]
 
 ### Contributing Tutorials