Simplify primality test

[bkalcho]

Think this primality test should be simplified. You may use the following algorithm:

// 2 is a special case of prime, and if n < 2 then skip it. For others see bellow
if n > 2 {
  for i := 2; i <= i/2; i++ {
    if n % i == 0 {
       break
      //It's not a prime
    }
  }
  // It's a prime
}

I am referring to the simplification of the following part of the code:

learngo/13-loops/exercises/10-crunch-the-primes/solution/main.go

Line 39 in e366d1a

for i, w := 5, 2; i*i <= n; {