type Login struct {
User     string `form:"user" json:"user" binding:"required"`
Password string `form:"password" json:"password" binding:"required"`

// Example for binding JSON ({"user": "manu", "password": "123"})
router.POST("/loginJSON", func(c *gin.Context) {
    var json Login
    if c.BindJSON(&json) == nil {
        if json.User == "manu" && json.Password == "123" {
            c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
        } else {
            c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
        }
    }
})