Do you mean a directory name cannot contain a hyphen (-)? Or perhaps you did mean a slash (/)?
I have never heard nor encountered about a package manager or filesystem that does not allow the use of hyphens.
The Go package name, which is potentially different than the manner if the directory it resides in. Go package names badly include hyphens (only Unicode letters)
The Go package name can be different than the name of the directory in which the package resides (although this is strongly discouraged). The directory may certainly contain hyphens, but the package name - the thing you see in the Go
package foo
statement - cannot contain hyphens... that's the actual package name, which can only contain unicode alpha-numerics.