docs: remove modules.md because it is not relevant with gopls enabled

This document only refers to issues that occur when gopls is disabled.
Remove it, and update any links that used to point to it. I didn't fix
links in the README, troubleshooting, or gopls files because those will
be modified soon. I did run the link checker on all of the files so I
fixed any other links I noticed.

Change-Id: If4db3cd555154410a41740c110543aaf210dacfe
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/284835
Trust: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
diff --git a/docs/debugging.md b/docs/debugging.md
index e41eda1..65c64e3 100644
--- a/docs/debugging.md
+++ b/docs/debugging.md
@@ -112,7 +112,7 @@
 buildFlags | Build flags to pass to the Go compiler. This corresponds to `dlv`'s `--build-flags` flag.
 dlvFlags   | Extra flags passed to `dlv`. See `dlv help` for the full list of supported flags. This is useful when users need to pass less commonly used or new flags such as `--only-same-user`, `--check-go-version`. Note that some flags such as `--log-output`, `--log`, `--init`, `--api-version` already have corresponding properties in the debug configuration, and flags such as `--listen` and `--headless` are used internally. If they are specified in `dlvFlags`, they may be ignored or cause an error.
 remotePath | If remote debugging (`mode`: `remote`), this should be the absolute path to the package being debugged on the remote machine. See the section on [Remote Debugging](#remote-debugging) for further details. [golang/vscode-go#45](https://github.com/golang/vscode-go/issues/45) is also relevant. Becomes the first mapping in substitutePath.
-substitutePath | An array of mappings from an absolute local path to an absolute remote path that is used by the debuggee. The debug adapter will replace the local path with the remote path in all of the calls. The mappings are applied in order, and the first matching mapping is used. This can be used to map files that have moved since the program was built, different remote paths, and symlinked files or directories. This is intended to be equivalent to the [substitute-path]((https://github.com/go-delve/delve/tree/master/Documentation/cli#config)(https://github.com/go-delve/delve/tree/master/Documentation/cli#config)) configuration, and will eventually configure substitute-path in Delve directly.
+substitutePath | An array of mappings from an absolute local path to an absolute remote path that is used by the debuggee. The debug adapter will replace the local path with the remote path in all of the calls. The mappings are applied in order, and the first matching mapping is used. This can be used to map files that have moved since the program was built, different remote paths, and symlinked files or directories. This is intended to be equivalent to the [substitute-path](https://github.com/go-delve/delve/tree/master/Documentation/cli#config) configuration, and will eventually configure substitute-path in Delve directly.
 cwd | The working directory to be used in running the program. If remote debugging (`mode`: `remote`), this should be the absolute path to the working directory being debugged on the local machine. See the section on [Remote Debugging](#remote-debugging) for further details. [golang/vscode-go#45](https://github.com/golang/vscode-go/issues/45) is also relevant.
 processId  | This is the process ID of the executable you want to debug. Applicable only when using the `attach` request in `local` mode.
 
diff --git a/docs/features.md b/docs/features.md
index 23b9966..3a1ba3d 100644
--- a/docs/features.md
+++ b/docs/features.md
@@ -210,7 +210,7 @@
 
 ### Code Coverage
 
-Show code coverage in the editor, either after running a test or on-demand. This can be done via the commands: [`Go: Apply Cover Profile`](commands.md#go-apply-cover-profile) and [`Go: Toggle Test Coverage in Current Package`](commands.go-toggle-test-coverage-in-current-package).
+Show code coverage in the editor, either after running a test or on-demand. This can be done via the commands: [`Go: Apply Cover Profile`](commands.md#go-apply-cover-profile) and [`Go: Toggle Test Coverage in Current Package`](commands.md#go-toggle-test-coverage-in-current-package).
 
 ## [Debugging](debugging.md)
 
diff --git a/docs/gopath.md b/docs/gopath.md
index 60c6346..23caa69 100644
--- a/docs/gopath.md
+++ b/docs/gopath.md
@@ -1,8 +1,14 @@
 # `GOPATH`
 
-The `GOPATH` environment variable is a fundamental part of writing Go code **without** [Go modules]. It specifies the location of your workspace, and it defaults to `$HOME/go`. A `GOPATH` directory contains `src`, `bin`, and `pkg` directories. Your code is typically located in the `$GOPATH/src` directory.
+The `GOPATH` environment variable is a fundamental part of writing Go code
+**without** [Go modules]. It specifies the location of your workspace, and it
+defaults to `$HOME/go`. A `GOPATH` directory contains `src`, `bin`, and `pkg`
+directories. Your code is typically located in the `$GOPATH/src` directory.
 
-If you are not familiar with Go and `GOPATH`, please first read about [writing Go code with `GOPATH`](https://golang.org/doc/gopath_code.html#GOPATH).
+If you are not familiar with Go and `GOPATH`, please first read about [writing
+Go code with `GOPATH`](https://golang.org/doc/gopath_code.html#GOPATH).
+
+**If you are just starting out with Go, we recommend [using Go modules](https://blog.golang.org/using-go-modules) instead of GOPATH.**
 
 ## Overview
 
@@ -21,7 +27,7 @@
 
 ## Setting `GOPATH`
 
-If you have chosen not to use [Go modules], you will need to configure your `GOPATH`. Modules have largely eliminated the need for a `GOPATH`, so if you're interested in using them, taking a look at the [modules documentation](modules.md) for the VS Code Go extension.
+If you have chosen not to use [Go modules], you will need to configure your `GOPATH`.
 
 Setting `GOPATH` is typically as simple as setting the environment variable once in your system's configuration. Take a look at the [Setting `GOPATH` Wiki](https://github.com/golang/go/wiki/SettingGOPATH) if you're unsure how to do this.
 
diff --git a/docs/modules.md b/docs/modules.md
deleted file mode 100644
index 899bb6b..0000000
--- a/docs/modules.md
+++ /dev/null
@@ -1,34 +0,0 @@
-# Modules
-
-This extension mostly supports [Go modules]. However, certain features have not been ported to work with modules. The reason for this is that the Go team is developing a language server, [`gopls`](gopls.md). This provides a comprehensive solution for [Go modules] support in all editors.
-
-However, as described in the [language server documentation](gopls.md), `gopls` is still in an alpha state, so it is **not yet** the default in VS Code Go. We understand that many users will not want to use alpha software, so this document describes how this extension works with [Go modules], **without the language server**.
-
-To learn how to use the language server with modules in VS Code, read our [`gopls` documentation](gopls.md).
-
-## Overview
-
-* [Missing features](#missing-features)
-  * [Formatting](#formatting)
-  * [References and rename](#references-and-rename)
-* [Performance](#performance)
-
-## Missing features
-
-As mentioned above, not all Go tools have been ported to work with modules. **Many tools will never be ported, as they are being replaced by [`gopls`](gopls.md).** [golang/go#24661](https://golang.org/issues/24661) contains up-to-date information about modules support in various Go tools.
-
-### Formatting
-
-The default [formatting](features.md#format-and-organize-imports) tool, [`goreturns`](tools.md#formatting), has not been ported to work with modules. As a result, you will need to change your [`"go.formatTool"`](settings.md#go.formatTool) setting for [formatting and import organization support](features.md#format-and-organize-imports). We recommend changing the value to `"goimports"` instead. Other options are also available, and you can read about them in the [format tools documentation](tools.md#formatting).
-
-### [References](features.md#find-references) and [rename](features.md#rename-symbol)
-
-The tools that provide these two features, [`guru`](tools.md#guru) and [`gorename`](tools.md#gorename), have not been updated for Go modules. Instead, they will be replaced by [`gopls`](gopls.md).
-
-## Performance
-
-[Go modules] introduced additional complexity to Go tooling. As a result, the performance of a number of tools is worse with modules enabled. Hopefully, you will not notice this too frequently.
-
-One case in which you may notice this is autocompletion. The best solution to this is to switch to [`gopls`](gopls.md), which makes use of an in-memory cache to provide results quickly.
-
-[Go modules]: https://blog.golang.org/using-go-modules
diff --git a/docs/nightly.md b/docs/nightly.md
index c18fe59..c6ddde8 100644
--- a/docs/nightly.md
+++ b/docs/nightly.md
@@ -2,7 +2,7 @@
 
 This master branch of this extension is built and published nightly through the [Go Nightly]. If you're interested in testing new features and bug fixes, you may be interested in switching to the [Go Nightly] extension. Also, if you file an issue, we may suggest trying out the fix in [Go Nightly].
 
-[Go Nightly] is the **preview** version of the Go extension, so it may be broken or unstable at times. The [Changelog](nightly/CHANGELOG.md) and [README](nightly/README.md) for [Go Nightly] can be found in the [docs/nightly](nightly/) directory.
+[Go Nightly] is the **preview** version of the Go extension, so it may be broken or unstable at times.
 
 ## Installation
 
diff --git a/docs/testing.md b/docs/testing.md
index 2a8abf2..0a72ed1 100644
--- a/docs/testing.md
+++ b/docs/testing.md
@@ -37,7 +37,9 @@
 
 This is the workflow triggered for every PR and commit made to our mirror repository on GitHub, [github.com/golang/vscode-go](https://github.com/golang/vscode-go). We use this CI system to run tests on platforms that GCB does not yet support. This workflow is not triggered by CLs sent via Gerrit yet.
 
-[`.github/workflows/ci.yml`](../.github/workflows/ci.yml) defines the GitHub Actions-based CI workflow.
+[`.github/workflows/test-long.yml`](../.github/workflows/test-long.yml) and
+[`.github/workflows/test-smoke.yml`](../.github/workflows/test-smoke.yml)
+define the GitHub Actions-based CI workflow.
 
 ### [Nightly Release](nightly.md)
 
diff --git a/docs/ui.md b/docs/ui.md
index 1287234..16f51cc 100644
--- a/docs/ui.md
+++ b/docs/ui.md
@@ -29,7 +29,7 @@
 
 ### Language Server Status
 
-`gopls` is the official Go [language server](https://langserver.org/) developed by the Go team. It was developed in response to the release of [Go modules](docs/modules.md), and it is the recommended approach when working with [Go modules](docs/modules.md) in VS Code.
+`gopls` is the official Go [language server](https://langserver.org/) developed by the Go team. It was developed in response to the release of [Go modules](docs/modules.md), and it is the recommended approach when working with Go modules in VS Code.
 
 When `gopls` is enabled, :zap: is displayed next to the Go version in the status bar and the `gopls` version is displayed in the menu.