Go Multiplication Assignment

// Syntax
LHS *= RHS

// Equivalent to
LHS = LHS * (RHS)

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Technical Characteristics

• LHS Assignability: The left-hand operand must be an assignable expression. In Go, this means the LHS must be either an addressable value (such as a variable, pointer indirection, slice element, or struct field) or a map index expression. While map elements are explicitly unaddressable (you cannot take their address using &m[key]), the language makes a specific exception allowing map index expressions on the left-hand side of assignments. The LHS cannot be a literal or a constant.
• Numeric Types: The *= operator is strictly defined for numeric types. Both operands must resolve to integers, floating-point numbers, or complex numbers.

var x int32 = 10
x *= 5        // Valid: 5 is an untyped constant implicitly converted to int32
x *= int32(2) // Valid: Explicitly matching types

var y float64 = 3.14
// x *= y     // Invalid: mismatched types int32 and float64

// The index expression `i` is evaluated only once.
slice[i] *= 10 

// The map index expression is evaluated only once.
m[key] *= 2

// Precedence preservation: evaluates as x = x * (A + B)
x *= A + B