gopl | 《Go 程序设计语言》

You might have some luck switching the delveConfig to use legacy mode:

Your code uses the format verb %x to print the hex values to the SVG's fill attribute:

for go I preferred vim go this is the good plugging for go.

e.ready is more known as done channel. this is a way to tell your ref functions that domething is ready by closing done (e.ready chan). <-e.ready is going to block until its done (closed).

so... reading this code it means next.

1. deliver waits for rediness signal.
2. call gets data for e.res (e.res.value, e.res.err = f(key)`)
3. call releas done channel by closing it (close(e.ready))
4. deliver can move throu block reading from <-e.ready and send data to response

Relevant: Access main package from other package

My best guess is that this was true when the book was written, but has since been made impossible. golang/go#4210 is the relevant issue and it seems the change that stopped it from working landed in mid-2015 while the book was published only a few months after.

The short answer is: You can run your object lambda function in a VPC as long as you allow it to route to s3-object-lambda..amazonaws.com through the internet, e.g. through a NAT gateway. You were on the right track and basically figured it out in your question already.

The S3 gateway interface endpoint is necessary to enable download of the input object.

When writing the result, the request goes to s3-object-lambda, which is technically a different service than S3 (at least on network level). AWS currently doesn't provide an interface endpoint for s3-object-lambda and the S3 gateway endpoint doesn't cover it either (which can be verified by comparing the IP address WriteGetObjectResponse request goes to and the routes created by the gateway endpoint).

So the only way is to route WriteGetObjectResponse requests via opened access to the internet. For future reference, one way to set this up is with a NAT gateway. Quoting AWS docs:

• The NAT gateway must be in a public subnet with a route table that routes internet traffic to an internet gateway.
• Your instance must be in a private subnet with a route table that routes internet traffic to the NAT gateway.
• Check that there are no other route table entries that route all or part of the internet traffic to another device instead of the NAT gateway.

In other words:

• Provision a public NAT Gateway in a public subnet and allocate it an elastic IP
• Make sure the public subnet has an internet gateway and the default route (0.0.0.0/0) points to it.
• Set up a default route (0.0.0.0/0) from the subnet hosting your lambda and point it to the NAT Gateway.

You're right that a NAT Gateway is priced by the hour, unfortunately, and you need one per subnet.

In theory, you could at least limit the egress with a security group to IP addresses of the s3-object-lambda service, but I'm not aware these IP ranges are published anywhere.

You can build a gopls with 1.18 go as described here: https://github.com/golang/tools/blob/master/gopls/doc/advanced.md#working-with-generic-code

This link posted in a now deleted comment - https://go.dev/ref/mod#mod-commands - provides an explanation for this seemingly (GO)PATH breaking change:-

Most go commands may run in Module-aware mode or GOPATH mode. In module-aware mode, the go command uses go.mod files to find versioned dependencies, and it typically loads packages out of the module cache, downloading modules if they are missing. In GOPATH mode, the go command ignores modules; it looks in vendor directories and in GOPATH to find dependencies.

As of Go 1.16, module-aware mode is enabled by default, regardless of whether a go.mod file is present. In lower versions, module-aware mode was enabled when a go.mod file was present in the current directory or any parent directory.

Further:-

Module-aware mode may be controlled with the GO111MODULE environment variable, which can be set to on, off, or auto.

I found the solution. It seems the problem happens when you copy your mod folder from an older installation. The solution is: