build: drop support for go1.8

fstest/fstests/bits.go

@@ -1,33 +0,0 @@
-//+build !go1.9
-
-package fstests
-
-func leadingZeros64(x uint64) int {
-	var n uint64 = 64
-
-	if y := x >> 32; y != 0 {
-		n = n - 32
-		x = y
-	}
-	if y := x >> 16; y != 0 {
-		n = n - 16
-		x = y
-	}
-	if y := x >> 8; y != 0 {
-		n = n - 8
-		x = y
-	}
-	if y := x >> 4; y != 0 {
-		n = n - 4
-		x = y
-	}
-	if y := x >> 2; y != 0 {
-		n = n - 2
-		x = y
-	}
-	if y := x >> 1; y != 0 {
-		return int(n - 2)
-	}
-
-	return int(n - x)
-}

fstest/fstests/bits_go1_9.go

@@ -1,11 +0,0 @@
-//+build go1.9
-
-package fstests
-
-import (
-	"math/bits"
-)
-
-func leadingZeros64(x uint64) int {
-	return bits.LeadingZeros64(x)
-}

fstest/fstests/fstests.go

@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"math/bits"
 	"os"
 	"path"
 	"path/filepath"
@@ -72,7 +73,7 @@ type SetUploadCutoffer interface {
 // NextPowerOfTwo returns the current or next bigger power of two.
 // All values less or equal 0 will return 0
 func NextPowerOfTwo(i fs.SizeSuffix) fs.SizeSuffix {
-	return 1 << uint(64-leadingZeros64(uint64(i)-1))
+	return 1 << uint(64-bits.LeadingZeros64(uint64(i)-1))
 }
 
 // NextMultipleOf returns a function that can be used as a CeilChunkSize function.