go2-language-changes: new template

This is intended for use with Go 2 language change proposals.

Change-Id: I45c7a85bb9eac752a5b3b17c55bebf2955b69f1d
Reviewed-on: https://go-review.googlesource.com/c/proposal/+/214820
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/go2-language-changes.md b/go2-language-changes.md
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+# Go 2 language change template
+Authors: Ian Lance Taylor, Robert Griesemer, Brad Fitzpatrick
+Last updated: January, 2020
+## Introduction
+We get more language change proposals than we have time to review
+Changing the language has serious consequences that could affect the
+entire Go ecosystem, so many factors come into consideration.
+If you just have an idea for a language change, and would like help
+turning it into a complete proposal, we ask that you not open an
+issue, but instead discuss the idea on a forum such as (the
+golang-nuts mailing
+Before proceeding with a full proposal, please review the requirements
+listed in the Go blog article [Go 2, here we
+come!](https://blog.golang.org/go2-here-we-come): Each language change
+proposal must:
+1. address an important issue for many people,
+1. have minimal impact on everybody else, and
+1. come with a clear and well-understood solution.
+If you believe that your proposal meets these criteria and wish to
+proceed, then in order to help with review we ask that you place your
+proposal in context by answering the questions below as best you can.
+You do not have to answer every question but please do your best.
+## Template
+- Would you consider yourself a novice, intermediate, or experienced Go programmer?
+- What other languages do you have experience with?
+- Would this change make Go easier or harder to learn, and why?
+- Has this idea, or one like it, been proposed before?
+  - If so, how does this proposal differ?
+- Who does this proposal help, and why?
+- Is this change backward compatible?
+  - Breaking the (Go 1 compatibility guarantee)[https://golang.org/doc/go1compat] is a large cost and requires a large benefit.
+- Show example code before and after the change.
+- What is the cost of this proposal? (Every language change has a cost).
+  - How many tools (such as vet, gopls, gofmt, goimports, etc.) would be affected?
+  - What is the compile time cost?
+  - What is the run time cost?
+- Can you describe a possible implementation?
+  - Do you have a prototype? (This is not required.)
+- How would the language spec change?
+- Orthogonality: how does this change interact or overlap with existing features?
+- Is the goal of this change a performance improvement?
+  - If so, what quantifiable improvement should we expect?
+  - How would we measure it?
+- Does this affect error handling?
+  - If so, how does this differ from [previous error handling proposals](https://github.com/golang/go/issues?utf8=%E2%9C%93&q=label%3Aerror-handling)?
+- Is this about generics?
+  - If so, how does this differ from the [the current design
+    draft](https://go.googlesource.com/proposal/+/master/design/go2draft-contracts.md)
+    and the [previous generics proposals](https://github.com/golang/go/issues?utf8=%E2%9C%93&q=label%3Agenerics)?
+## What to avoid
+If you are unable to answer many of these questions, perhaps your
+change has some of these characteristics:
+- Your proposal simply changes syntax from X to Y because you prefer Y.
+- You believe that Go needs feature X because other languages have it.
+- You have an idea for a new feature but it is very difficult to implement.
+- Your proposal states a problem rather than a solution.
+Such proposals are likely to be rejected quickly.
+## Thanks
+We believe that following this template will save reviewer time when
+considering language change proposals.