A few things:
- You’re using a very old version of JuMP.
- You should consult the documentation: Introduction · JuMP
- There are also lots of examples: JuMP.jl/examples at v0.20.1 · jump-dev/JuMP.jl · GitHub.
- I recommend you start with the Quickstart Guide, which shows how to use GLPK.
- Take another read of the PSA.
- In particular, point 1 describes how to format your code.
- Point 4 is also important: simplify your code as much as possible. Try to reduce it to the minimum amount of code necessary to reproduce the error.