implemented state pattern

README.md

@@ -21,6 +21,7 @@
     - [Chain of responsibility](#chain-of-responsibility)
     - [Strategy](#strategy)
     - [Observer](#observer)
+    - [State](#state)
 - [Concurrency patterns](#concurrency-patterns)
 
 ---
@@ -82,5 +83,8 @@ Strategy lets the algorithm vary independently from clients that use it.
 ### Observer
 Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically
 
+### State
+Allow an object alter its behavior when its internal state changes. The object will appear on change its class
+
 ## Concurrency patterns
 Pattenrs for concurrent work and parallel execution in Go.

behavioral/state/state.go

@@ -0,0 +1,55 @@
+package state
+
+import (
+	"fmt"
+)
+
+type State interface {
+	executeState(c *Context)
+}
+
+type Context struct {
+	StepIndex int
+	StepName  string
+	Current   State
+}
+
+type StartState struct{}
+
+func (s *StartState) executeState(c *Context) {
+	c.StepIndex = 1
+	c.StepName = "start"
+	c.Current = &StartState{}
+}
+
+type InprogressState struct{}
+
+func (s *InprogressState) executeState(c *Context) {
+	c.StepIndex = 2
+	c.StepName = "inprogress"
+	c.Current = &InprogressState{}
+}
+
+type StopState struct{}
+
+func (s *StopState) executeState(c *Context) {
+	c.StepIndex = 3
+	c.StepName = "stop"
+	c.Current = &StopState{}
+}
+
+func StateDemo() {
+	context := &Context{}
+
+	startState := &StartState{}
+	startState.executeState(context)
+	fmt.Println("state: ", context)
+
+	inprState := &InprogressState{}
+	inprState.executeState(context)
+	fmt.Println("state: ", context)
+
+	stopState := &StopState{}
+	stopState.executeState(context)
+	fmt.Println("state: ", context)
+}