Unable to call a go-gin middleware

I am learning and trying to create a simple api using go-gin framework.

I tried to create a middleware for validation but when I call it it says validations.signupValidator() is undefined.

Coming from nodejs express things seems a bit different, thanks in advance for your help

Middleware:

package validations

import (
    "github.com/bihire/ikaze_server_app/entity"
    "net/http"
    "github.com/gin-gonic/gin"
    "gopkg.in/validator.v2"
)


func signupValidator(ctx *gin.Context) {
    var user entity.User
    // if err := ctx.ShouldBindJSON(&user); err != nil {
    //    ctx.JSON(http.StatusBadRequest, gin.H{
    //        "error": err.Error(),
    //    })
    // }

    if err := validator.Validate(user); err != nil {
        ctx.JSON(http.StatusBadRequest, gin.H{
            "error": err.Error(),
        })
    }
}

calling it like

package routes

import (
    "github.com/gin-gonic/gin"
    "github.com/bihire/ikaze_server_app/service"
    "github.com/bihire/ikaze_server_app/controller"
    "github.com/bihire/ikaze_server_app/validations"
)

var (
    userController controller.UserController = controller.New(UserService)
)

func Routes(route *gin.Engine) {
    auth := route.Group("/api/auth")
    {
        
        auth.POST("login", gin.Logger(), validations.signupValidator(), func(ctx *gin.Context) {
            ctx.JSON(200, userController.Save(ctx))
        })
    }
}

You must first export the signupValidation since it is on another package. To do that just change to uppercase: SignupValidation

package validations

import (
    "github.com/bihire/ikaze_server_app/entity"
    "net/http"
    "github.com/gin-gonic/gin"
    "gopkg.in/validator.v2"
)


func SignupValidator(ctx *gin.Context) {
    var user entity.User
    // if err := ctx.ShouldBindJSON(&user); err != nil {
    //    ctx.JSON(http.StatusBadRequest, gin.H{
    //        "error": err.Error(),
    //    })
    // }

    if err := validator.Validate(user); err != nil {
        ctx.JSON(http.StatusBadRequest, gin.H{
            "error": err.Error(),
        })
    }
}

Second: A gin middleware is made with this signature func (ctx *gin.Context). You could do in 2 ways:

First, if you don't want to change the Signup

package routes

import (
    "github.com/gin-gonic/gin"
    "github.com/bihire/ikaze_server_app/service"
    "github.com/bihire/ikaze_server_app/controller"
    "github.com/bihire/ikaze_server_app/validations"
)

var (
    userController controller.UserController = controller.New(UserService)
)

func Routes(route *gin.Engine) {
    auth := route.Group("/api/auth")
    {
        
        auth.POST("login", gin.Logger(), validations.SignupValidator, func(ctx *gin.Context) {
            ctx.JSON(200, userController.Save(ctx))
        })
    }
}

Or, changing Signup:

func SignupValidator(ctx *gin.Context) gin.HandlerFunc {
    return func(c *gin.Context) {
      var user entity.User
      // if err := ctx.ShouldBindJSON(&user); err != nil {
      //    ctx.JSON(http.StatusBadRequest, gin.H{
      //        "error": err.Error(),
      //    })
      // }

      if err := validator.Validate(user); err != nil {
          ctx.JSON(http.StatusBadRequest, gin.H{
              "error": err.Error(),
          })
          return
      }
      c.Next()
   }
}

Then, you can use with validations.signupValidator()

See an example here: https://github.com/gin-gonic/gin#custom-middleware