Add lint and go generate steps to CI (#254)

* Add lint and go generate stages to CI

Add CI step to verify `go generate` was run on repo.
Add linter stage to CI along with linter config file,
`.golangci.yml`.
Will likely prefer revive over static-check.

Updated README Contributing section on linting requirements.

Added sequence ordering to make sure lint and go generate stages run
before tests and build.
This way, build and tests are not run on code that could potentially:

    1. not build due to `gofmt` issues;
    2. contain bugs;
    3. have to be re-submitted after issues are fixed; or
    4. contain outdated Win32 syscall or other auto-generated files.

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

* Fixed linter issues

Code changes to satisfy linters:

 - Ran `gofmt -s -w` on repo.
 - Broke up long lines.
 - When possible, changed names with incorrect initialism formatting
   - Added exceptions for exported variables.
 - Added exceptions for ALL_CAPS_WITH_UNDERSCORES code.
   - Switched to using `windows` or `syscall` definitions if possible;
     especially if some constants were unused.
 - Added `_ =` to satisfy error linter, and acknowledge that errors are
   being ignored.
 - Switched to using `errors.Is` and `As` in places, elsewhere added
   exceptions if error value was known to be `syscall.Errno`.
 - Removed bare returns.
 - Prevented variables from being overshadowed in certain places
   (ignoring cases of overshadowing `err`).
 - Renamed variables and functions (eg, `len`, `eventMetadata.bytes`) to
   prevent shadowing pre-built functions and imported pacakges.
 - Removed unused method receivers.
 - Added exceptions to certain unused (unexported) constants and
   functions.
   - Deleted unused `once` from `pkg/etw.providerMap`.
 - Renamed `noop.go` files to `main_other.go` or `doc.go`, to better fit
   style recommendations.
 - Added exceptions for non-secure use of SHA1 and weak crypto
   libraries.
 - Replaced `ioutil` with `io` and `os` (and `t.TempDir` in tests).
 - Added fully exhaustive checks for `switch` statements in `pkg/etw`.
 - Defined constant strings for `tools/mkwinsyscall`.
 - Removed unnecessary conversions.
 - Made sure `context.Cancel` was called.

Additionally, added `//go:build windows" constraints on files with
unexported code, since linter will complain about unused code on
non-Windows platforms.

Added a stub `main() {}` for `mkwinsyscall` for non-Windows builds, just in
case `//go:generate` directives are added to OS-agnostic files.

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

* PR: spelling, constants, fuzzing

Moved HVSocket fuzzing tests to separate file with go 1.18 build
constraint.

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

pkg/etw/eventmetadata.go

@@ -1,3 +1,5 @@
+//go:build windows
+
 package etw
 
 import (
@@ -10,6 +12,8 @@ type inType byte
 
 // Various inType definitions for TraceLogging. These must match the definitions
 // found in TraceLoggingProvider.h in the Windows SDK.
+//
+//nolint:deadcode,varcheck // keep unused constants for potential future use
 const (
 	inTypeNull inType = iota
 	inTypeUnicodeString
@@ -47,6 +51,8 @@ type outType byte
 
 // Various outType definitions for TraceLogging. These must match the
 // definitions found in TraceLoggingProvider.h in the Windows SDK.
+//
+//nolint:deadcode,varcheck // keep unused constants for potential future use
 const (
 	// outTypeDefault indicates that the default formatting for the inType will
 	// be used by the event decoder.
@@ -81,11 +87,11 @@ type eventMetadata struct {
 	buffer bytes.Buffer
 }
 
-// bytes returns the raw binary data containing the event metadata. Before being
+// toBytes returns the raw binary data containing the event metadata. Before being
 // returned, the current size of the buffer is written to the start of the
 // buffer. The returned value is not copied from the internal buffer, so it can
 // be mutated by the eventMetadata object after it is returned.
-func (em *eventMetadata) bytes() []byte {
+func (em *eventMetadata) toBytes() []byte {
 	// Finalize the event metadata buffer by filling in the buffer length at the
 	// beginning.
 	binary.LittleEndian.PutUint16(em.buffer.Bytes(), uint16(em.buffer.Len()))
@@ -95,7 +101,7 @@ func (em *eventMetadata) bytes() []byte {
 // writeEventHeader writes the metadata for the start of an event to the buffer.
 // This specifies the event name and tags.
 func (em *eventMetadata) writeEventHeader(name string, tags uint32) {
-	binary.Write(&em.buffer, binary.LittleEndian, uint16(0)) // Length placeholder
+	_ = binary.Write(&em.buffer, binary.LittleEndian, uint16(0)) // Length placeholder
 	em.writeTags(tags)
 	em.buffer.WriteString(name)
 	em.buffer.WriteByte(0) // Null terminator for name
@@ -118,7 +124,7 @@ func (em *eventMetadata) writeFieldInner(name string, inType inType, outType out
 	}
 
 	if arrSize != 0 {
-		binary.Write(&em.buffer, binary.LittleEndian, arrSize)
+		_ = binary.Write(&em.buffer, binary.LittleEndian, arrSize)
 	}
 }
 
@@ -151,13 +157,17 @@ func (em *eventMetadata) writeTags(tags uint32) {
 }
 
 // writeField writes the metadata for a simple field to the buffer.
+//
+//nolint:unparam // tags is currently always 0, may change in the future
 func (em *eventMetadata) writeField(name string, inType inType, outType outType, tags uint32) {
 	em.writeFieldInner(name, inType, outType, tags, 0)
 }
 
 // writeArray writes the metadata for an array field to the buffer. The number
 // of elements in the array must be written as a uint16 in the event data,
-// immediately preceeding the event data.
+// immediately preceding the event data.
+//
+//nolint:unparam // tags is currently always 0, may change in the future
 func (em *eventMetadata) writeArray(name string, inType inType, outType outType, tags uint32) {
 	em.writeFieldInner(name, inType|inTypeArray, outType, tags, 0)
 }
@@ -165,6 +175,8 @@ func (em *eventMetadata) writeArray(name string, inType inType, outType outType,
 // writeCountedArray writes the metadata for an array field to the buffer. The
 // size of a counted array is fixed, and the size is written into the metadata
 // directly.
+//
+//nolint:unused // keep for future use
 func (em *eventMetadata) writeCountedArray(name string, count uint16, inType inType, outType outType, tags uint32) {
 	em.writeFieldInner(name, inType|inTypeCountedArray, outType, tags, count)
 }