When I define field names with numbers in front of them, there is an error when running

[anthony-zh]

env := map[string]interface{}{ "1greet": "Hello, %v!", "names": []string{"world", "you"}, "sprintf": fmt.Sprintf, }

program, err := expr.Compile(`sprintf(1greet, names[0])`, expr.Env(env))
if err != nil {
    panic(err)
}

output, err := expr.Run(program, env)
if err != nil {
    panic(err)
}

fmt.Print(output) // Hello, world!

=== RUN TestExpr2 --- FAIL: TestExpr2 (0.00s) panic: bad number syntax: "1g" (1:10) | sprintf(1greet, names[0]) | .........^ [recovered] panic: bad number syntax: "1g" (1:10) | sprintf(1greet, names[0]) | .........^

[mdmcconnell]

Variable names can not begin with a number, so the parser will believe they are numbers and raise the error you have noticed. If those variables are defined in your environment, and you need to access them, you can wrap in $env, like $env["1greet"].

[antonmedv]

@mdmcconnell is right. Use $env:

$env["1greet"]