Here it is! I wanted a progress the other night so I wrote this up.

in.go

@@ -0,0 +1,66 @@
+// in is a commandline utility that sleeps for a specified amount of time
+// while displaying a progress bar.
+//
+// Ex: in 2m30s && run_a_command
+//
+// Author: Andrew Kallmeyer
+// Copyright 2021 Google LLC.
+// SPDX-License-Identifier: Apache-2.0
+package main
+
+import (
+  "os"
+  "fmt"
+  "time"
+  "strings"
+)
+
+const (
+  BarLen = 40
+  BarFilled = '='
+  BarEmpty = '-'
+  Step = time.Second
+)
+
+const ClearLine = "\033[K" // ESC[K, the ECMA-48 CSI code for Erase line. See man 4 console_codes
+
+func progressbar(elapsed, total int64) string {
+  const realBarLen = BarLen-2 // to account for the [ and ]
+
+  // Solve for progress: total / BarLen = elapsed / progress
+  progress := int(elapsed / (total / realBarLen))
+  if progress < 0 || progress > realBarLen {
+    fmt.Fprintln(os.Stderr, "Bad miscaculation:", progress, elapsed, total, realBarLen)
+    os.Exit(2)
+  }
+
+  var b strings.Builder
+  b.WriteRune('[')
+  for i := 0; i < progress; i+=1 {
+    b.WriteRune(BarFilled)
+  }
+  for i := 0; i < (realBarLen - progress); i+=1 {
+    b.WriteRune(BarEmpty)
+  }
+  b.WriteRune(']')
+  return b.String()
+}
+
+func main() {
+  if len(os.Args) < 2 {
+    fmt.Fprintf(os.Stderr, "Usage example: %v 2m30s\n", os.Args[0])
+    os.Exit(127)
+  }
+  sleeptime, err := time.ParseDuration(os.Args[1])
+  if err != nil {
+    fmt.Fprintln(os.Stderr, "Invalid duration:", os.Args[1])
+    os.Exit(1)
+  }
+  for elapsed := 0*time.Second; elapsed < sleeptime; elapsed += Step {
+    fmt.Fprintf(os.Stderr, "\r%s %v/%v%s",
+      progressbar(elapsed.Milliseconds(), sleeptime.Milliseconds()),
+      elapsed, sleeptime, ClearLine)
+    time.Sleep(Step)
+  }
+  fmt.Fprintf(os.Stderr, "\rDing!%s\n", ClearLine)
+}