Update quic-go dependency to support go 1.20 (#2292)

vendor/github.com/quic-go/qpack/varint.go

@@ -0,0 +1,66 @@
+package qpack
+
+// copied from the Go standard library HPACK implementation
+
+import "errors"
+
+var errVarintOverflow = errors.New("varint integer overflow")
+
+// appendVarInt appends i, as encoded in variable integer form using n
+// bit prefix, to dst and returns the extended buffer.
+//
+// See
+// http://http2.github.io/http2-spec/compression.html#integer.representation
+func appendVarInt(dst []byte, n byte, i uint64) []byte {
+	k := uint64((1 << n) - 1)
+	if i < k {
+		return append(dst, byte(i))
+	}
+	dst = append(dst, byte(k))
+	i -= k
+	for ; i >= 128; i >>= 7 {
+		dst = append(dst, byte(0x80|(i&0x7f)))
+	}
+	return append(dst, byte(i))
+}
+
+// readVarInt reads an unsigned variable length integer off the
+// beginning of p. n is the parameter as described in
+// http://http2.github.io/http2-spec/compression.html#rfc.section.5.1.
+//
+// n must always be between 1 and 8.
+//
+// The returned remain buffer is either a smaller suffix of p, or err != nil.
+// The error is errNeedMore if p doesn't contain a complete integer.
+func readVarInt(n byte, p []byte) (i uint64, remain []byte, err error) {
+	if n < 1 || n > 8 {
+		panic("bad n")
+	}
+	if len(p) == 0 {
+		return 0, p, errNeedMore
+	}
+	i = uint64(p[0])
+	if n < 8 {
+		i &= (1 << uint64(n)) - 1
+	}
+	if i < (1<<uint64(n))-1 {
+		return i, p[1:], nil
+	}
+
+	origP := p
+	p = p[1:]
+	var m uint64
+	for len(p) > 0 {
+		b := p[0]
+		p = p[1:]
+		i += uint64(b&127) << m
+		if b&128 == 0 {
+			return i, p, nil
+		}
+		m += 7
+		if m >= 63 { // TODO: proper overflow check. making this up.
+			return 0, origP, errVarintOverflow
+		}
+	}
+	return 0, origP, errNeedMore
+}