'@ID' tags are not properly validated for uniqueness

[sreya]

Describe the bug

Two routes with the same path may share an ID without an error being thrown. This is because the map holding
paths will be overwritten with the latest route see here

To Reproduce
Create two endpoints that have the same path. For example

// @ID duplicate-id
// @Router /api/foo/{id} [get]

// @ID duplicate-id
// @Router /api/foo/{id} [delete]

Expected behavior
No two routes should be able to share an ID.

Your swag version
e.g. 1.7.0

Your go version
go version go1.15.6 linux/amd64

Desktop (please complete the following information):

• OS: [linux]
• Browser: [chrome]
• Version: [22]

[ubogdan]

This is an OSS project, please feel free to do a PR if you feel like it's really important to you.