Add stack implementation in Go (blakeembrey#180)

Author: itsanna

solutions/go/stack.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+  "errors"
+  "fmt"
+  "log"
+  "sync"
+)
+
+type Stack struct {
+  lock  sync.Mutex // concurrency-safe stack
+  stack []int
+}
+
+func New() *Stack {
+  return &Stack{
+    lock:  sync.Mutex{},
+    stack: make([]int, 0),
+  }
+}
+
+func (s *Stack) Push(n int) {
+  s.lock.Lock()
+  defer s.lock.Unlock()
+  s.stack = append(s.stack, n)
+  fmt.Printf("pushed %v to the stack \n", n)
+}
+
+func (s *Stack) Pop() (int, error) {
+  s.lock.Lock()
+  defer s.lock.Unlock()
+
+  length := len(s.stack)
+  if length == 0 {
+    err := errors.New("stack is empty")
+    return 0, err
+  }
+
+  // extract the last item in stack
+  last := s.stack[length - 1]
+
+  // remove the last item in stack
+  s.stack = s.stack[:length - 1]
+
+  fmt.Printf("removed %v from the stack \n", last)
+  return last, nil
+}
+
+func main() {
+  stack := New()
+  wg := sync.WaitGroup{}
+  concurrency := 3
+
+  // concurrently push values to the stack
+  wg.Add(concurrency)
+  for i := 0; i < concurrency; i++ {
+    go func(n int) {
+      stack.Push(n + 10)
+      wg.Done()
+    }(i)
+  }
+
+  // sequentially pop value off the stack
+  wg.Wait()
+  for j := 0; j < 3; j++ {
+    _, err := stack.Pop()
+    if err != nil {
+      log.Fatal(err)
+    }
+  }
+}