c.ShouldBind() maybe will stack overflow

[vvlgo]

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Description

I used a structure, and the type of a field is itself. When I upload form data and receive it with shoudbind, the stack overflows. Please use the following code to reproduce. I hope to solve this problem. Thank you

How to reproduce

package main

import (
	"github.com/gin-gonic/gin"
)
//post form-data a
func main() {
	r := gin.Default()
	r.POST("/test", TestShoudbind)
	r.Run(":8080")
}

func TestShoudbind(c *gin.Context){
	a := A{}
	c.ShouldBind(&a)
	c.JSON(200,a)
}

type A struct {
	B string `form:"b" json:"b"`
	L *A     `json:"l"`
}

Expectations

postman 
post http://localhost:8080/test
form-data
b test111

json:{"b":"test111","l":nil}

Actual result

postman 
post http://localhost:8080/test
form-data
b test111

runtime: goroutine stack exceeds 1000000000-byte limit
fatal error: stack overflow

Environment

• go version:1.3.5
• gin version (or commit ref):1.4.0
• operating system:macos10.15.2

[JellyZhang]

Duplicate of #1978
This problem is caused by circular reference.
You can ignore this field with tag form:"-" like this:

type A struct {
	B string `form:"b" json:"b"`
	L *A     `form:"-" json:"l"`
}