# go: github.com/foo/bar@v1.2.3: reading github.com/foo/bar/go.mod at revision v1.2.3: module not found

- **ID:** `go/go-mod-tidy-fails-with-module-not-found`
- **Domain:** go
- **Category:** module_error
- **Verification:** ai_generated
- **Fix Rate:** 92%

## Root Cause

The specified module version does not exist in the module proxy or upstream repository, often due to a typo in version tag or a deleted release.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| go1.18 | active | — | — |
| go1.19 | active | — | — |
| go1.20 | active | — | — |

## Workarounds

1. **Check available versions: go list -m -versions github.com/foo/bar; then use a valid version.** (95% success)
   ```
   Check available versions: go list -m -versions github.com/foo/bar; then use a valid version.
   ```
2. **Use the latest version by removing @v1.2.3: go get github.com/foo/bar@latest** (85% success)
   ```
   Use the latest version by removing @v1.2.3: go get github.com/foo/bar@latest
   ```
3. **Set GONOSUMCHECK and GONOSUMDB env vars to bypass proxy restrictions: export GONOSUMCHECK=*; export GONOSUMDB=*; then go mod tidy** (70% success)
   ```
   Set GONOSUMCHECK and GONOSUMDB env vars to bypass proxy restrictions: export GONOSUMCHECK=*; export GONOSUMDB=*; then go mod tidy
   ```

## Dead Ends

- **** — -e flag only suppresses error output, module still missing. (90% fail)
- **** — go.sum regeneration requires valid module version; missing version persists. (70% fail)