package main

import (
	"fmt"

	"github.com/gin-gonic/gin"
)

type R struct {
	C string `form:"c" binding:"required"`
}

func main() {
	g := gin.Default()
	g.POST("/hello", func(c *gin.Context) {
		if err := c.BindJSON(&R{}); err != nil {
			fmt.Println(err, len(c.Errors))
		}
	})
	g.Run(":9000")
}

$ curl --request POST '127.0.0.1:9000/hello' --data '' 

print EOF 1.
Expect: 
`Key: 'R.C' Error:Field validation for 'C' failed on the 'required' tag 0` or `invalid request` or `empty body`