Go, often referred to as Golang, strictly enforces that all declared variables and imported packages within a program must be actively used; otherwise, the compiler will issue an error. This design choice is fundamental to the language's philosophy, aiming to maintain rapid compilation speeds and ensure code clarity. As noted by Jon Calhoun in a recent tweet, "In Go, every variable and import in your code must be used, otherwise the compile will throw an error."
The rationale behind this strict rule is rooted in Go's commitment to long-term build efficiency and program readability. Unused elements can indicate potential bugs or lead to "code rot" over time, slowing down development and increasing maintenance overhead. The Go team believes this approach trades "short-term convenience for long-term build speed and program clarity," as detailed in the official Go documentation.
Despite its benefits, this strictness can sometimes pose challenges during active development, especially when code is in flux or undergoing debugging. Developers might temporarily comment out sections of code, leading to previously used variables or imports becoming unused and triggering compilation errors. This can interrupt workflow and necessitate immediate adjustments to the code.
To address these specific scenarios, Go provides the blank identifier, represented by an underscore (_). This special placeholder allows developers to explicitly signal to the compiler that a variable or import is intentionally unused, thereby silencing the error. Calhoun's tweet highlights this utility, stating, "In those cases the blank identifier (_) can be used as a placeholder."
The blank identifier is commonly employed for various purposes, such as ignoring return values from functions, importing packages solely for their side effects (e.g., registering a database driver), or temporarily holding a variable during the development phase. While some developers find the compiler's strictness initially "annoying," many come to appreciate how it fosters cleaner, more efficient codebases by preventing accumulation of dead or irrelevant code.