As simple http server with Gin

httpserver.go

import (
    "github.com/gin-gonic/gin"
    "github.com/gin-contrib/sessions"
    "github.com/gin-contrib/sessions/cookie"
)

func main() {
    r := gin.Default()
    store := cookie.NewStore([]byte("secret"))
    r.Use(sessions.Sessions("mysession", store))

    r.POST("/login", func(c *gin.Context) {
        // You would authenticate the submitted user/password here
        session := sessions.Default(c)
        session.Set("user", "username") // Set user session
        session.Save()
        c.JSON(200, gin.H{"message": "Logged in"})
    })

    r.GET("/protected", func(c *gin.Context) {
        session := sessions.Default(c)
        user := session.Get("user")
        if user == nil {
            c.JSON(401, gin.H{"message": "Unauthorized"})
            return
        }
        c.JSON(200, gin.H{"message": "Welcome!", "user": user})
    })

    r.Run()
}