Revert "migration: go 1.21"

This reverts commit 33d41338ef.

hub/updater/limitedreader.go

@@ -3,6 +3,8 @@ package updater
 import (
 	"fmt"
 	"io"
+
+	"golang.org/x/exp/constraints"
 )
 
 // LimitReachedError records the limit and the operation that caused it.
@@ -33,7 +35,7 @@ func (lr *limitedReader) Read(p []byte) (n int, err error) {
 		}
 	}
 
-	p = p[:min(lr.n, int64(len(p)))]
+	p = p[:Min(lr.n, int64(len(p)))]
 
 	n, err = lr.r.Read(p)
 	lr.n -= int64(n)
@@ -54,3 +56,12 @@ func LimitReader(r io.Reader, n int64) (limited io.Reader, err error) {
 		n:     n,
 	}, nil
 }
+
+// Min returns the smaller of x or y.
+func Min[T constraints.Integer | ~string](x, y T) (res T) {
+	if x < y {
+		return x
+	}
+
+	return y
+}