use go 1.12

Signed-off-by: hongming <talonwan@yunify.com>

vendor/github.com/bifurcation/mint/syntax/README.md

@@ -0,0 +1,84 @@
+TLS Syntax
+==========
+
+TLS defines [its own syntax](https://tlswg.github.io/tls13-spec/#rfc.section.3)
+for describing structures used in that protocol.  To facilitate experimentation
+with TLS in Go, this module maps that syntax to the Go structure syntax, taking
+advantage of Go's type annotations to encode non-type information carried in the
+TLS presentation format.
+
+For example, in the TLS specification, a ClientHello message has the following
+structure:
+
+~~~~~
+uint16 ProtocolVersion;
+opaque Random[32];
+uint8 CipherSuite[2];
+enum { ... (65535)} ExtensionType;
+
+struct {
+    ExtensionType extension_type;
+    opaque extension_data<0..2^16-1>;
+} Extension;
+
+struct {
+    ProtocolVersion legacy_version = 0x0303;    /* TLS v1.2 */
+    Random random;
+    opaque legacy_session_id<0..32>;
+    CipherSuite cipher_suites<2..2^16-2>;
+    opaque legacy_compression_methods<1..2^8-1>;
+    Extension extensions<0..2^16-1>;
+} ClientHello;
+~~~~~
+
+This maps to the following Go type definitions:
+
+~~~~~
+type protocolVersion uint16
+type random [32]byte
+type cipherSuite uint16 // or [2]byte
+type extensionType uint16
+
+type extension struct {
+  ExtensionType extensionType
+  ExtensionData []byte `tls:"head=2"`
+}
+
+type clientHello struct {
+	LegacyVersion            protocolVersion
+	Random                   random
+	LegacySessionID          []byte        `tls:"head=1,max=32"`
+	CipherSuites             []cipherSuite `tls:"head=2,min=2"`
+	LegacyCompressionMethods []byte        `tls:"head=1,min=1"`
+	Extensions               []extension   `tls:"head=2"`
+}
+~~~~~
+
+Then you can just declare, marshal, and unmarshal structs just like you would
+with, say JSON.
+
+The available annotations right now are all related to vectors:
+
+* `head`: The number of bytes of length to use as a "header"
+* `min`: The minimum length of the vector, in bytes
+* `max`: The maximum length of the vector, in bytes
+
+## Not supported
+
+* The `select()` syntax for creating alternate version of the same struct (see,
+  e.g., the KeyShare extension)
+
+* The backreference syntax for array lengths or select parameters, as in `opaque
+  fragment[TLSPlaintext.length]`.  Note, however, that in cases where the length
+  immediately preceds the array, these can be reframed as vectors with
+  appropriate sizes.
+
+
+QUIC Extensions Syntax
+======================
+syntax also supports some minor extensions to allow implementing QUIC.
+
+* The `varint` annotation describes a QUIC-style varint
+* `head=none` means no header, i.e., the bytes are encoded directly on the wire.
+  On reading, the decoder will consume all available data.
+* `head=varint` means to encode the header as a varint