fix: quickstart dont work

[yunfan]

the default quickstart section do not work for the command order
this would failed beginner and prevent their going on learning, so after i fingered out the fixing, i just want to contributed it back
to you

[kesonan]

Maybe deleted go mod init should be work.

[yunfan]

go version go1.22.3 linux/amd64

[kesonan]

I can generate code by executing goctl api new greet, but an error ocurred while running the project, do you mean it can not work beacuse of this issue block your learning step?

[yunfan]

@kesonan not only the failing blocked my learning path but also the steps has other issues in the middle, please check the following screenshots

as showed above, if i began with a fresh directory, it will has problem when running go mod init which required my gaving the mod name , and after i gaved the mod name to init, it then caused bigger problem when running the sample code

and i paste the generated code here
sample.zip