Go 程序员的演变，最后的 “Rob Pike” 这个梗看懂了吗？

package fac
func Factorial(n int) int {
  res := 1
  for i := 1; i <= n; i++ {
    res *= i
  }
  return res
}

package fac
func Factorial(n int) int {
  if n == 0 {
    return 1
  } else {
    return Factorial(n - 1) * n
  }
}

package fac
func Factorial(n interface{}) interface{} {
  v, valid := n.(int)
  if !valid {
    return 0
  }
  res := 1
  for i := 1; i <= v; i++ {
    res *= i
  }
  return res
}

package fac
import "sync"
func Factorial(n int) int {
  var (
    left, right = 1, 1
    wg sync.WaitGroup
  )
  wg.Add(2)
  pivot := n / 2
  go func() {
    for i := 1; i < pivot; i++ {
      left *= i
    }
    wg.Done()
  }()
  go func() {
    for i := pivot; i <= n; i++ {
      right *= i
    }
    wg.Done()
  }()
  wg.Wait()
  return left * right
}

package fac
func Factorial(n int) <-chan int {
  ch := make(chan int)
  go func() {
    prev := 1
    for i := 1; i <= n; i++ {
      v := prev * i
      ch <- v
      prev = v
    }
    close(ch)
  }()
  return ch
}

package fac
/**
 * @see https://en.wikipedia.org/wiki/Factorial
 */
type IFactorial interface {
  CalculateFactorial() int
}
// FactorialImpl implements IFactorial.
var _ IFactorial = (*FactorialImpl)(nil)
/**
 * Used to find factorial of the n.
 */
type FactorialImpl struct {
  /**
   * The n.
   */
  n int
}
/**
 * Constructor of the FactorialImpl.
 *
 * @param n the n.
 */
func NewFactorial(n int) *FactorialImpl {
  return &FactorialImpl{
    n: n,
  }
}
/**
 * Gets the n to use in factorial function.
 *
 * @return int.
 */
func (this *FactorialImpl) GetN() int {
  return this.n
}
/**
 * Sets the n to use in factorial function.
 *
 * @param n the n.
 * @return void.
 */
func (this *FactorialImpl) SetN(n int) {
  this.n = n
}
/**
 * Returns factorial of the n.
 *
 * @todo remove "if" statement. Maybe we should use a factory or somthing?
 *
 * @return int.
 */
func (this *FactorialImpl) CalculateFactorial() int {
  if this.n == 0 {
    return 1
  }
  n := this.n
  this.n = this.n - 1
  return this.CalculateFactorial() * n
}

package fac
// Factorial returns n!.
func Factorial(n int) int {
  res := 1
  for i := 1; i <= n; i++ {
    res *= i
  }
  return res
}

package fac
// Factorial returns n!.
func Factorial(n int) int {
  res := 1
  for i := 1; i <= n; i++ {
    res *= i
  }
  return res
}