Gin Depends on a non-existent version of yaml.v2

Description

Not specifying any particular version a go build fails due to...

gopkg.in/yaml.v2@v2.2.8: reading gopkg.in/yaml.v2/go.mod at revision v2.2.8: unknown revision v2.2.8

How to reproduce

package main

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

func main() {
    g := gin.Default()
    g.GET("/hello/:name", func(c *gin.Context) {
        c.String(200, "Hello %s", c.Param("name"))
    })
    g.Run(":9000")
}

Expectations

An executable binary.

Actual result

$ go mod init gintest
go: creating new go.mod: module gintest
$ go build .
go: finding module for package github.com/gin-gonic/gin
go: found github.com/gin-gonic/gin in github.com/gin-gonic/gin v1.6.3
go: github.com/gin-gonic/gin@v1.6.3 requires
    gopkg.in/yaml.v2@v2.2.8: reading gopkg.in/yaml.v2/go.mod at revision v2.2.8: unknown revision v2.2.8

Environment

• go version: go1.15.5 linux/amd64
• gin version (or commit ref): not specifying
• operating system: CentOS 8