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| 1 | +package main |
| 2 | + |
| 3 | +import ( |
| 4 | + "encoding/json" |
| 5 | + "log" |
| 6 | + "os" |
| 7 | + "os/exec" |
| 8 | + "regexp" |
| 9 | + "slices" |
| 10 | +) |
| 11 | + |
| 12 | +func main() { |
| 13 | + log.Println("Listing all available Go versions using `go list -m -versions go`...") |
| 14 | + cmd := exec.Command("go", "list", "-m", "-versions", "-json=Versions", "go") |
| 15 | + cmd.Env = append(os.Environ(), "GOPROXY=https://proxy.golang.org") |
| 16 | + out, err := cmd.Output() |
| 17 | + if err != nil { |
| 18 | + log.Fatalln(err) |
| 19 | + } |
| 20 | + |
| 21 | + log.Println("Parsing output of `go list -m -versions go`...") |
| 22 | + var module struct { |
| 23 | + Versions []string `json:"Versions"` |
| 24 | + } |
| 25 | + if err := json.Unmarshal(out, &module); err != nil { |
| 26 | + if err, ok := err.(*exec.ExitError); ok { |
| 27 | + log.Println("STDERR:", string(err.Stderr)) |
| 28 | + } |
| 29 | + log.Fatalln(err) |
| 30 | + } |
| 31 | + |
| 32 | + if len(module.Versions) == 0 { |
| 33 | + log.Fatalln("No versions found!") |
| 34 | + } |
| 35 | + |
| 36 | + // Versions are returned sorted in ascending SemVer order. |
| 37 | + slices.Reverse(module.Versions) |
| 38 | + |
| 39 | + log.Println("Looking for a release candidate version...") |
| 40 | + goVersions := make([]string, 2, 3) |
| 41 | + goVersions[0] = "oldstable" |
| 42 | + goVersions[1] = "stable" |
| 43 | + |
| 44 | + // Versions are represented in a form that isn't quite regular SemVer. |
| 45 | + versionRe := regexp.MustCompile(`^(1\.\d+)(\.\d+)?(?:(beta|rc)(\d+))?$`) |
| 46 | + for _, v := range module.Versions { |
| 47 | + parts := versionRe.FindStringSubmatch(v) |
| 48 | + if parts == nil { |
| 49 | + log.Fatalln("Encountered unsupported version string:", v) |
| 50 | + } |
| 51 | + major, minor, pre, serial := parts[1], parts[2], parts[3], parts[4] |
| 52 | + if pre == "" { |
| 53 | + // Not a pre-release version, there is no "next" release available. |
| 54 | + log.Println("No relevant release candidate version found!") |
| 55 | + break |
| 56 | + } |
| 57 | + if pre != "rc" { |
| 58 | + // Not a release candidate; we don't test against those. |
| 59 | + continue |
| 60 | + } |
| 61 | + // †he minor is omitted when it's ".0"; but actions/setup-go needs it. |
| 62 | + if minor == "" { |
| 63 | + minor = ".0" |
| 64 | + } |
| 65 | + rcVersion := major + minor + "-" + pre + "." + serial |
| 66 | + log.Println("Found release candidate version:", rcVersion) |
| 67 | + goVersions = append(goVersions, rcVersion) |
| 68 | + // We have what we came here for, we can break out of the loop now. |
| 69 | + break |
| 70 | + } |
| 71 | + |
| 72 | + log.Println("Encoding output as a JSON array...") |
| 73 | + enc := json.NewEncoder(os.Stdout) |
| 74 | + if err := enc.Encode(goVersions); err != nil { |
| 75 | + log.Fatalln(err) |
| 76 | + } |
| 77 | + |
| 78 | + log.Println("Done!") |
| 79 | +} |
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